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Audacity Plugins

This site features download links to various plugins for Audacity, which can be used to extend Audacity's functionality to better match your workflow.

On this site you can find download links for , , , and more. If you'd like to download many plugins at once, you also can try entire .

All plugins in the realtime effects section can be used instantly and non-destructively from the effects panel in Audacity.

realtime effects

Plugin Suites

Families of plugins by the same authors

Muse FX

A collection of essential effects. Contains a Chorus, Compressor, De-esser, Delay, Master, Noise Gate, Pitch Fix, Reverb, Rotary, and two EQ effects.

MuseFX is a free and expanding collection of high quality plugins for Audacity, MuseScore 4 and any VST3 compatible host. MuseFX brings the tools you need to elevate your mix to a higher level.

Available for all platforms

GVST

A set of simple VST effects, most known for the GSnap (auto-tune) effect.

Available for Windows and macOS

MFreeFXBundle

A collection of 37 effects in categories like Analysis, Saturation & distortion, Dynamics, Equalization, Mastering, Mixing, Pitch and others.

ToneBoosters

Powerful plugins for any type of audio mixing: eq, dynamics, reverb, and more.

Details

"Demo" mode is fully functional except for preset saving. You can use Audacity's preset system instead.

What is Included:

Barricade 4 : Limiter

Kilohearts Essentials

Kilohearts Essentials is free collection of 30+ plugins.

Available for Windows only

Reaplugs

A selection of some effects found in Reaper.

Intel OpenVINO

Music separation, remix and generation, noise suppression, and transscription

Available for macOS

MacOS already ships with a range of Audio Unit effects which you can try out

Available for Linux

swh Plugins

A set of LADSPA effects. They can be found in most Linux repositories.

Calf Studio Gear

An LV2 plugin suite featuring a wide array of plugins for audio mixing and mastering. As of version 0.90.0 there are 47 plugins in the suite.

Note: The virtual instruments included are not supported in Audacity.

The Calf plugins can be found in the repositories of most Linux distributions, additionally, compilation instructions can be found here:

Pitch and Tempo

MuseFX PitchFix

An easy to use pitch correction/snapping/autotune effect. Part of the Muse FX pack.

Details

See the pack for installation instructions.

Has modes optimized for male/female voices and more, and can snap to major, minor and even more rare scales (eg Lydian).

MAutoPitch

Automatic vocal tuning effect, part of the pack

Details

MAutoPitch is a simple but great sounding automatic tuning and pitch correction plugin designed for vocals and other monophonic instruments. Besides making the audio more in-tune, MAutoPitch also provides creative features such as formant shift and stereo-expansion.

Advanced GUI

Delay and Reverb

MuseFX Delay

An easy to use, versatile delay effect, part of the Muse FX pack.

Details

See the pack for installation instructions.

MuseFX Reverb

An easy to use, versatile reverb effect, part of the pack.

Details

See the pack for installation instructions.

ReaDelay

A multi-tap delay effect, part of ReaPlugs.

Details

Information From the vendor:

Multi-tap delay, no practical limit on tap count

MConvolutionEZ

An easy-to-use highly optimized convolution reverb, part of the pack

Details

MConvolutionEZ is an easy-to-use highly optimized convolution reverb. Comes with lots of impulse responses for rooms, halls, plates, guitar cabinets, effects.

Advanced GUI

MCharmVerb

A Lush algorithmic reverb effect, , part of the pack

Details

MCharmVerb is a great sounding lush algorithmic reverb based on the MTurboReverb engine.

Advanced GUI

OrilRiver

A free algorithmic stereo reverb

Details

12 early reflections variations
5 reverb tail variations

TAL-Reverb-4

A plate reverb with a vintage 80's character

Details

Information from the developer website:

Modulated vintage reverb sound.

U-he Protoverb

A natural sounding reverb based on the concept of a room simulator

Details

Information from the developer website:

Protoverb is an experimental room simulator reverb. Most algorithmic reverbs try to avoid resonances or model the reflections of sound from a room’s walls. Protoverb does the opposite. It builds up as many room resonances as possible, modelling the body of air in the room. No need to modulate or colour the signal. The result is a very natural sounding reverberation with interesting characteristics:

Notes held for a longer time tend to build up resonance, as if the air takes a while to get excited Multiple instruments remain distinct, without disappearing in a wash When you play a short melody, the room seems to repeat a ghost echo of that melody These properties are found in churches and large halls, but are rarely in conventional algorithmic reverbs.

Voxengo OldSkoolVerb

OldSkoolVerb offers you a comprehensive set of parameters permitting you to achieve various reverbs ranging from plate reverb to room reverb to hall reverb sound.

Details

Information from the developer website:

Plate, room, and hall reverbs

Valhalla Supermassive

ValhallaSupermassive lets you create massive reverbs, harmonic echoes and space sounds

Details

Information from the developer website:

ValhallaSupermassive is based around feedback delay networks. The individual delays can have up to 2 second of delay time, with user control over the delay lengths, the feedback, how the delays mix with each other, and the modulation rate and depth of the delays. The sonic results range from choruses and flangers, to echoes that fade in and out over time, to massive lush reverbs, and onwards to weird spatial effects that have to be heard to be believed.

Distortion

MBitFun

A distortion tool, part of the pack

Details

Modulation

MuseFX Chorus

An easy to use chorus effect. Part of the Muse FX pack.

Details

See the pack for installation instructions.

MuseFX Rotary

An easy to use Rotary/Leslie effect. Part of the pack.

Details

See the pack for installation instructions.

Valhalla Space Modulator

A modulator with 11 different algorithms.

Details

COMPATIBILITY:

WINDOWS: WINDOWS 7/8/10

MRingModulator

Classic two oscillators ring-modulation effect, part of the pack

Details

MRingModulator performs classic ring-modulation effects using one or two oscillators. With a clean interface that gives easy access to more advanced controls like our adjustable phase difference and shape features, including editable custom waveforms and harmonics.

Advanced GUI

AI plugins

Intel OpenVINO

A set of AI-enabled effects, generators, and analyzers. These AI features run 100% locally on your PC 💻 -- no internet connection necessary! OpenVINO™ is used to run AI models on supported accelerators found on the user's system such as CPU, GPU, and NPU.

🎵 -- Separate a mono or stereo track into individual stems -- Drums, Bass, Vocals, & Other Instruments.
🧹 -- Removes background noise from an audio sample.
🎶 -- Generates music from a text prompt or continues an existing song
🎤 -- Uses to generate a label track containing the transcription or translation for a given selection of spoken audio or vocals.

NVIDIA Broadcast

A virtual device that sits between your microphone and Audacity and other programs which allows you to use an AI denoiser.

Caution: NVIDIA Broadcast only works on Windows machines with a NVIDIA RTX GPU.

Further, it only works on spoken word content; musical content is treated as noise and filtered out.

Details

Requires NVIDIA GeForce RTX 2060, Quadro RTX 3000, TITAN RTX or higher

Full setup guide:

Technically, NVIDIA Broadcast isn't a plugin but a virtual device. You will find it in Audacity's audio settings as an input. It does not show up in the Plugin Manager.

Nyquist Plugins

Generator Plugins

Various generator-type Nyquist plugins. Licensed under GPL v2 unless otherwise noted.

Noise Generators

Harmonic Noise

Generates approximately harmonic tones by mixing narrow bands of noise

Details

Special Effect Generators

Binaural Tones with Surf 2

A sine tone of one constant frequency is generated in the left channel of a stereo track, and a series of changing tones of slightly different frequencies are generated in the right.

Details

Author:

A sine tone of one constant frequency is generated in the left channel of a stereo track, and a series of changing tones of slightly different frequencies are generated in the right. The differences between the left- and right-channel frequencies are termed "beat frequencies". In addition, a stereo "surf" noise is generated based on . This is a lower-frequency "rushing" sound compared with "hissing" white noise.

Parameters:

Left channel tone frequency: [50 - 1000 Hz, default 100].

Surf-LFO

An LFO surf generator.

Details

Author:

LFO Surf generator. A signal whose frequency is generally below the human ear's ability to hear as a tone, usually 20 cycles per second [Hz]. Generates mono or stereo surf which sweeps between a lower and upper filter frequency. Stereo surf also sweeps back-and-forth somewhere between the left and right audio channels. To generate stereo surf, first open a new stereo track in Audacity

Parameters:

1. Mono or stereo surf: [1=mono 2=stereo] Mono surf is heard only in the center between the two speakers, or in the middle of your head when wearing headphones. Stereo surf sweeps back-and-forth somewhere between the two audio channels, depending on the next setting, Stereo Spread.

Surf-Oxy

A surf generator inspired by Jean-Michel Jarre's album Oxygene.

Details

Author:

Jean-Michel Jarre put out a hauntingly beautiful electronic album in 1976, Oxygene. One section of this album had a repeating surf sound: a sweep from the right to the left audio channel, a pause, and then a deep crash in the right channel. After another pause, this cycle repeated many times. Very relaxing to listen to. This sound generator plugin emulates that surf cycle, in either mono or stereo.

Start a new session of Audacity. To generate stereo surf, first open a blank stereo track

Parameters:

Instrument Sound Generators

Fire and Explosion sounds

Emulates a Korg MS-10 synthesizer patch.

Details

Author:

Emulates a Korg MS-10 synthesizer patch.

Parameters:

Audio type: [0=fire 1=explosion, default=1]
Sound duration: [0.1 to 60 seconds, default=3]
Attack time: [0 to 500 milliseconds, default=50]

KLSTRBAS

KLSTRBAS (for "cluster bass") generates dense sounds by combining several waveforms with a fixed frequency ratio between them.

Details

Author: Steven Jones.

KLSTRBAS (for "cluster bass") generates dense sounds by combining several waveforms with a fixed frequency ratio between them. Early Roland drum machines created cymbal sound in part by combining multiple square waves with non-integral frequency ratios. The combined signal was then high-pass filtered to produce a very dense cluster of high frequency harmonics. The genesis of KLSTRBAS was a failed attempt to create cymbal sounds using this technique.

Parameters:

Pluck (Hz)

Pluck generates a synthesized pluck tone with abrupt or gradual fade-out.

Details

Author: and Steve Daulton.

Pluck generates a synthesized pluck tone with abrupt or gradual fade-out. The sound is the same as the that is shipped with Audacity, except that the pitch of the note is determined by entering a frequency in Hz (cycles per second) rather than a MIDI note.

Parameters:

Risset Bell

Simulates a realistic bell tone based on the pioneering work of Jean Claude Risset.

Details

Author: Steven Jones.

Simulates a realistic bell tone based on the pioneering work of Jean Claude Risset. This plugin is an adaptation of a demonstration lisp file by Pedro Jose Morales contained in the standard Nyquist distribution.

Parameters:

Generator Utilities

Nyquist Generate Prompt

Nyquist Generate Prompt makes it easy for Nyquist developers to test their code for "Generate" plugins in one step.

Details

Effect Plugins

Analyzers

Contributing

Developing your own plugins and scripts

Plugins

Audacity supports the following formats:

Nyquist (Lisp or SAL) Audacity's built-in scripting format. Allows for easy generation of UI elements and already is tuned to Audacity's needs. Note that this plugin format is not supported as realtime effects. Documentation:

Creating your own Nyquist Plugins

Basics

Tutorials

Additional resources

Audacity custom themes

Audacity supports custom themes in the form of ImageCache.png files.

Installation instructions can be found here:

Audacity themes forum

Themes created by the Audacity community

EQ curves

Weighted curves

A-weighted curve

A-weighting is a commonly used curve defined in the International standard IEC 61672:2003. It was originally developed for measuring low level noise in audio equipment.

1KB

A-weighting.xml

Open

External scripts

External scripts don't run within Audacity itself. Instead, they communicate with it using mod-script-pipe.

Further information can be found here:

vinyl2digital

For batch processing of vinyls

Macro Tutorial

Nyquist-Macros are a special kind of Nyquist plugin that instruct Audacity to perform tasks using Audacity's scripting interface.

To use this feature effectively, it is necessary to use the correct commands and syntax, and also understand that when Nyquist is used in this way, Nyquist is not allowed, or able, to modify the project. Nyquist-Macros may instruct Audacity to modify the project, but unlike ''ordinary'' Nyquist plugins, Nyquist cannot itself modify the project.

Nyquist-Macros are potentially far more powerful than normal Macros in that they may make use of logic, loops and conditionally executing code, rather than only running through a simple list. They can also accept user input via the usual Nyquist plugin GUI, and most other features of Nyquist plugins.

About This Tutorial

Nyquist Macros are a fairly advanced topic, so this tutorial is aimed at users with an intermediate to advanced level of experience with Nyquist programming.

In this tutorial, we will be reimplementing Audacity's generator as a Nyquist Macro. During the course of the tutorial, many of the abilities and core concepts of Nyquist Macros will be discussed, along with tips and potential pitfalls to watch out for in your own programming.

Nyquist Macros are a powerful extension of Audacity's features. With great power comes great responsibility. Nyquist Macros bypass much of Audacity's built-in validation, so it is relatively easy to pass invalid commands that can cause Audacity to crash. Test your Nyquist Macros thoroughly before using them for important production work.

Overview

Audacity provides a rich set of scripting commands, which are documented in the section of the Audacity manual. These commands may be sent from Nyquist, to tell Audacity what to do, using the function call "AUD-DO". As a very simple example, Nyquist can tell Audacity to start playing by sending the command "Play:"

(aud-do "Play")

Some things to note:

The command "Play:" is a string (text).
The command is case sensitive. It must be capitalized exactly as stated in the .
The Nyquist function is AUD-DO, which like any other Nyquist function is case insensitive, and usually written in lower case in code.

As Nyquist cannot modify the project when used to send Macro scripting commands, most Nyquist-Macros will be written as "tool" type plugins.

Passing Commands to Audacity

The examples in this section may be run in the , but ensure that you make a in an audio track first.

As described above, the "AUD-DO" function takes exactly one argument (parameter), which is the command that will be sent to Audacity. However, we may sometimes want to send a command that has multiple parameters. For example, to generate a 10 second, 200 Hz, 0.5 amplitude sine tone, the Macro Scripting command is:

Tone: Frequency=200 Amplitude=0.5 Waveform="Sine"

With AUD-DO we can send the command, including it's parameters, as one string:

(aud-do "Tone: Frequency=200 Amplitude=0.5 Waveform=Sine")

Using the above example, the macro command string could be passed as the value of a variable:

As with other Nyquist commands, a string argument does not need to be a , it may be a variable that evaluates to a string.

(setf command "Tone: Frequency=200 Amplitude=0.5 Waveform=Sine") (aud-do command)

In this slightly more complex example we use the command to construct the command string. This approach is very useful if scripting command parameters are to be generated programmatically or obtained from user input.

If we incorporate this code in an installable Nyquist Macro, we see that we are getting close to re-implementing Audacity's generator as a Nyquist macro.

Here is a simplified implementation of Audacity's Tone Generator:

Some important things to note in this example Nyquist Macro:

The plugin type is "tool". If it were set as a "generate" type, running the plugin without a track would crash because of the duplicate attempt to create a new track (once from the plug-in being a generate type, and again from the Audacity scripting command).
This simplified version does not provide a "Duration" control, so the generated tone will be the length of the selection (if there is a selection), or 30 seconds (default).
In the Scripting command, the Waveform parameter must be quoted because its value may include a space. We therefore use

Importing Scripting Functions

If you are familiar with Nyquist's LISP syntax, you will have noticed that the syntax described above is not very Lisp-like. The ''magic string'' commands are case sensitive, and constructing the strings is inelegant. However, for many of the scripting commands, a lisp equivalent exists.

Each of these functions have names beginning '''AUD-''', suffixed with the scripting command name. The scripting command parameters are passed as keyword arguments.

There is a small performance penalty when using these LISP syntax commands, so for performance critical applications (such as batch processing many small files), it may be preferred to use the AUD-DO versions.''

In Audacity 2.3.2 and later, the following scripting commands have equivalent LISP functions:

effects.
effects.
.

Tip: Remember that Nyquist Macros cannot call Nyquist effects.

Example: The scripting command for Audacity's built-in "Amplify" effect is:

Amplify: Ratio=<number>

The equivalent imported LISP function for Audacity's built-in Amplify effect is:

(aud-amplify :ratio <number>)

In both versions, the ratio is a floating point number representing the gain on a linear scale. If we want to Amplify by -3 dB, we can apply the Amplify effect:

Tip: Although the imported function names, and keys are case insensitive, note that if the keyword value is a string, the value is case sensitive.

In this next code sample, we reproduce the simple "Tone" generator from above, using the imported AUD-TONE function:

Length of Generated Sounds

Unlike Nyquist's generator functions, Audacity's built-in do not have a parameter for the duration of the sound that is generated. Instead, the duration is set by the length of the track selection. If there is no track selection, then the length defaults to 30 seconds.

One limitation of Nyquist plugins that we cannot yet work around, is that the plugin UI is not dynamic and cannot be changed programmatically. Where as Audacity's built-in Tone generator will automatically show the length of the selected audio, this is not yet possible for Nyquist plugins. As a compromise solution, we can:

Add a "Duration" control.
If there is no selection, create a selection of the length specified by the Duration control.
If there is a selection, ignore the Duration control and generate into the selection.

Note: In order to generate audio into a selection, there has to be a ''track'' selection before running the generate command. It is not enough to have a time selection without a track being selected.

As we want to mimic the behaviour of Audacity's Tone generator, we need to handle cases where:

There is a selection in an audio track.
There is a time selection but no track selection.
There is a track selection but no time selection.

While is is possible to find what is selected using the scripting command , a simpler way is to use the Nyquist global property list *SELECTION*.

In Audacity 2.3.0 and later, there is a "[Nyquist_Plug-ins_Widgets#Time_Widget time widget]", which greatly simplifies handling durations, and is in keeping with Audacity's built-in effects.

;control duration "Duration" time "" 30 0 nil

Then we want to check if an audio track is selected, and if not, add a new track. Note that there isn't a LISP function for adding a new track, so we fall back on AUD-DO instead:

And to handle the time selection:

Putting It All Together

The completed Nyquist Macro plug-in:

Tips

When using built-in effects or "Scriptable" commands, it is recommended to use the optional LISP functions. Not only are they more Lisp-like and convenient to use, they also provide a little more error checking, which can be very helpful when debugging. Note however that there is a small performance penalty when using these LISP syntax commands. For performance critical applications (such as batch processing many small files), it may be preferred to use the AUD-DO versions.

Be flexible in your thinking. Scripting commands are available for many, but not all of Audacity's functions. If you need to do something that appears to be missing from the available commands, consider other ways to achieve the desired result.

If you get stuck, ask for help. As with other aspects of Nyquist programming, support requests may be made on the Nyquist board of the .

Delay and Reverb

A delay effect is similar to an echo, in that the sound is repeated (after a brief time delay) one or more times after the original sound.

Bouncing Ball Delay

A delay plugin where, like a bouncing ball, the bounces get faster and faster.

Details

Author:

A delay plugin where, like a bouncing ball, the bounces get faster and faster. You can set time that the bounces increase in speed with each delay, the number of bounces, and how much in dB the sound decreases with each bounce.

Parameters:

Decay amount [dB]: how much quieter each bounce is.

Bouncing Ball Delay with Panning

Combines the with a panning effect.

Details

Author:

Combines the Bouncing Ball Delay with a panning effect. A delay effect in which the echo get faster, like a bouncing ball. Each echo is panned further from center by the designated amount.

This plugin has bugs and may produce unpredictable results with some settings, but is basically functional.

Parameters:

Bouncing Ball Delay with Tone Shift

Combines the with Tone Shift plugins.

Details

Author:

Combines the Bouncing Ball Delay and Delay with Tone Shift plugins. A delay effect in which the echoes get faster, like a bouncing ball. Each echo is shifted in pitch by the designated amount in semitones plus cents (hundredths of a semitone).

Parameters:

Reverse Bouncing Ball Delay

The fastest bounces come first, gradually slowing down - reverse of the effect.

Details

Author:

The fastest bounces come first, gradually slowing down - reverse of the bouncing ball delay effect. Includes normalisation. Note: The latest available delay plugin 3 in includes reverse bouncing ball delay without normalisation, and also includes pitch shifting.

Parameters:

Reverse Bouncing Ball Delay with Tone Shift

The fastest bounces come first - reverse of the , and each bounce is tone shifted.

Details

Author:

The fastest bounces come first - reverse of the bouncing ball delay, and each bounce is tone shifted. Note: The latest available delay plugin in Audacity includes reverse bouncing ball delay and pitch shifting.

Parameters:

Chimes delay

Adds random delay to your audio, and randomly changes the pitch of each delay if you specify a note list.

Details

Author: Steve Daulton

Based on chimesdelay.ny by

Adds random delay to your audio, and randomly changes the pitch of each delay if you specify a note list (which is where the name 'Chimes Delay' comes from).

Each number in the note list indicates how many semitones your audio should be pitch shifted (along with matching tempo shift). For example, 0 indicates no pitch shift, 12 indicates a rise of 12 semitones (one octave), -5 indicates drop of 5 semitones (like going from C down to G below that C note).

Delay BPM with Panning

Applies a delay effect based on a specified tempo (beats per minute), with optional panning and filtering of the delayed sound.

Details

Author: Felipe Zanabria (based on code by Steve Daulton)

Applies a delay effect based on a specified tempo (beats per minute), with optional panning and filtering of the delayed sound. Requires a stereo track.

Parameters:

Delay with High-Pass Filter

Applies a high-pass filter to a delay so that with each subsequent delay, the filter's cut-off frequency is increased.

Details

Author:

Applies a high-pass filter to a delay so that with each subsequent delay, the filter's cut-off frequency is increased. A high-pass filter attenuates sound below a given cut off frequency, therefore when this plugin is applied, each delay sounds increasingly thin and lacking bass. Applied to a voice, it makes each delay sounds like it's increasingly coming from a telephone.

Parameters:

Delay with Low-Pass Filter

Applies a low-pass filter to a delay so that with each subsequent delay, the filter's cut-off frequency is reduced.

Details

Author:

Applies a low-pass filter to a delay so that with each subsequent delay, the filter's cut-off frequency is reduced. A low-pass filter attenuates sound above a given cut off frequency, therefore when this plugin is applied, each delay sounds to have increasing bass. To the author, this has the psychoacoustic effect of each delay sounding further and further away.

Based on an effect heard in a popular Cher tune in the late 1990s or later.

Parameters:

Delay with Pitch Change

A delay plugin except, each delay is pitch shifted.

Details

Author:

A delay plugin except, each delay is pitch shifted. Note that pitch changes are accompanied by a corresponding change in duration of each delay.

Parameters:

Delay with Stereo Flip

This is a stereo delay effect: with each delay, the stereo channels are flipped from left to right and vice versa.

Details

Author:

This is a stereo delay effect: with each delay, the stereo channels are flipped from left to right and vice versa. Inspired by a sound effect heard in the opening track of Mike Oldfield's "Songs From Distant Earth."

Parameters:

Delay with Tone Shift

Similar to pitchshift.ny except you can define in semitones how much each delay is to be pitch shifted.

Details

Author:

Similar to pitchshift.ny except you can define in semitones how much each delay is to be pitch shifted. A shift of 1 semitone means each delay is increased in pitch by 1 semitone, a shift of -1 means a decrease of 1 semitone. Includes whole semitones plus semitone cents (hundredths of a semitone).

Both plugins are best applied to relatively short duration audio, or few number of delays for longer audio. Otherwise Audacity will be working a long time. Same thing seems to happen if there is already pitch shifting within the audio.

Modulation Effects

Dual Tape Decks

Simulates two tape decks playing identical tapes, but out of synchronization with each other.

Details

Author:

Simulates two tape decks playing identical tapes, but out of synchronization with each other. Written to produce an effect I heard in the late 1970s: I recorded then played identical audio on two mono tape decks. There was an amazing "whooshing" effect as one tape deck "caught up" with and passed what the other tape deck was playing. This plugin allows the "whooshing" to go back and forth. Different effects are made using mono-sounding vs. "true" stereo audio.

The plugin can produce some interesting stereo effects, though note that due to the greater "cross-talk" of speakers, listening in speakers and headphones will sound different. Stereo flanger-like effects can be made by (for example) applying dualtapedecks.ny to audio, applying Stereo Butterfly (static) with a spread value of zero (sounds mono after applying), then applying dualtapedecks.ny a second time with the same settings as the first time. This plugin will work on mono audio as well, but the only effect will be rising and falling changes in pitch and tempo.

Parameters:

LFO frequency: [Hz, 0.001 to 25.000]
Starting phase: [degrees, -180 to +180, default 0]
Phase difference: [degrees, 0 to 360, default 180]

Flanger (linear)

Details

Author:

Unlike a regular flanger (which cycles up and down repeatedly), this plugin creates a single high-frequency flange, and you can set the position of that high-frequency point, anywhere between the start and end of the selection and beyond. The plugin works by mixing the original selected audio with a slightly shrunk (shorter) version of itself.

Works on mono and stereo audio.

Parameters:

Isochronic modulator

A variable tremolo plugin customized with controls for length and fade in/out speed of each pulse.

Details

Author: Steve Daulton

A variable tremolo plugin customized with controls for length and fade in/out speed of each pulse. The modulation frequency (speed) and depth transform gradually from the initial settings to the final settings. A modified square wave is used as the modulation waveform.

The effect is typically applied to a single tone to create . The author supplies the plugin only as a demonstration of audio processing without endorsing or claiming any relevance to the theory or practice of .

Parameters:

Random Amplitude Modulation

Similar to , this time playing around with the volume knob.

Details

Author:

Similar to Random Panning, this time playing around with the volume knob. Because of the way the random signal is generated, the lower the maximum speed is, the higher the depth factor must be to produce a similar depth of amplitude changes.

Parameters:

Random Pitch Modulation

Randomly modulates the pitch of your audio.

Details

Author:

Randomly modulates the pitch of your audio. As with other randomly-controlled effects, the the lower the maximum speed is, the higher the depth factor must be to produce a similar depth of random changes. This effect works on mono and stereo audio. In stereo, each channel has different random pitch modulation applied. "Max pitch mod depth" can be explained thus: at higher warping depth settings, pitch mod depth should be made higher, otherwise there will be momentary periods without pitch changes. With lower warping depth settings this does not happen, and the effect can be re-applied repeatedly to give further random pitch changes.

Parameters:

Ring Modulator

A ring modulator is a tremolo effect, but instead of using an LFO to amplitude modulate audio, an audio signal is used.

Details

Author:

A ring modulator is a tremolo effect, but instead of using an LFO to amplitude modulate audio, an audio signal is used. The result is a combination of the sum of and the difference between the two input signal frequencies e.g., two sine waves of 440 Hz and 660 Hz produce a result of 220 Hz (difference) and 1100 Hz (sum).

This plugin also allows use of triangle, sawtooth and pulse waveforms, so the results are the sums and differences between the harmonics of the modulating signal and harmonics of the signal being modulated.

Parameters:

Variable Tremolo

This plugin produces a "Tremolo" effect in which the frequency and depth of the tremolo varies from an initial setting to a final setting.

Details

Author: Steve Daulton

This plugin produces a "Tremolo" effect in which the frequency and depth of the tremolo varies from an initial setting to a final setting. The effect makes the loudness "wobble" and you can set the speed of the wobble and the amount that it wobbles for both the start of the selection and the end of the selection.

Parameters:

Vibrato

This effect applies vibrato (a regular pulsating change of pitch) to the selected audio.

Details

Author: Steve Daulton

This effect applies vibrato (a regular pulsating change of pitch) to the selected audio. The speed at which the sound pulsates can be varied over time by selecting an initial speed and a final speed. The vibrato speed will smoothly transition from the initial speed to the final speed. For a constant speed vibrato, set the Initial and Final speed settings to the same value.

The depth of the vibrato (amount of pitch variance) can varied over time by setting initial, mid point and final depth values. The vibrato depth begins at the initial value and smoothly transitions to the mid-point value, then to the final value. The time at which the mid-point depth is achieved can be adjusted. When "Mid point position" is set to 50%, the mid-point depth is reached half way through the selection. Smaller "Mid point position" values shift the mid-point earlier, so that the transition in depth from "Initial" to "Mid point" occurs more quickly, and the transition from "Mid point" to "Final" occurs more slowly. Similarly, larger values shift the mid-point later.

This plugin is intended for use on short selections. Due to cumulative rounding errors, the sound quality will gradually deteriorate on long selections, so it is recommended to apply the effect to selections that are less than 1 minute.

File Button Tutorial

This tutorial provides a description and examples of how to create and use a File-Button Widget in Nyquist Plugins.

The File-Button Widget provides a means to select one or more files via a graphical file browser.

Overview

For some plugins it is necessary to read from or write to files. In order to do this, it is necessary to define precisely which file is required, where the file is located, and whether it is required for read access or write access (for read access, the file must exist, whereas for write access this is not always a requirement).

Prior to the availability of the File-Button Widget, file names could be hard coded into the Nyquist script, or a text box could be provided for the user to enter the name of the file. Hard coded file paths lack flexibility, are platform specific (a path starting with "C:\" does not work on Mac or Linux), and may point to locations that do not exist on some machines. While a text box may provide a better solution than hard coding a file path, it remains inconvenient and prone to user error, especially for long file paths. The File-Button Widget was introduced in Audacity 2.3.0 to solve these problems, by providing access to a graphical "file browser window" similar to using File menu > Open or File menu > Save in other applications.

Syntax and Appearance

The File-Button Widget, as shown above, has an editable text input field that allows a file path to be typed (or pasted). After the text input field is a button that launches a file browser. Below is an example of the familiar file browser window on Windows 10.

Note that selecting a file in this file browser does NOT open the file.

When a file is selected in the file browser window, the full name and path of the selected file is passed to the Nyquist script as the value of the File-Button Widget variable.

Widget Arguments (Parameters)

The syntax for creating a File-Button Widget is similar to all other .

;control : Start of header statement. The leading semicolon ";" (or dollar character "$") tells Nyquist to treat this line as a comment and ignore it. The keyword "control" tells Audacity to create a GUI widget to be used by the Nyquist script.
variable-name : [symbol] The variable name that will be set.
text-left : [string] Text on the left side of the widget.

Magic Strings

The final three arguments, default-file-path, wildcard-filters, and flags, use special keywords that define the behavior of the File-Button Widget and the associated File Browser.

Note that unlike Nyquist symbols, these keywords are case sensitive.
The "Windows", "macOS" and "Linux" examples below refer to standard file paths for modern operating systems, though may be different on some machines.
"<username>" is the name of the computer user's account (log-in name).

Default File Path

"default file path" supports the keywords:

*home*" : The current user's .
- Windows: C:\Users\<username>\
- macOS:

These keywords may be combined with a file name to specify which file to open. For example, if you want the default file to be called "sample-data.txt", and you want the default location to be the default "Documents" path, you could write the default file path parameter as: "*default*/sample-data.txt".

File paths should be quoted with double quotes, otherwise spaces in file name will fail. If no file path is provided, the default is "default". If no file name is provided, the default file name is "untitled". The default file extension is taken from the wildcard-filters.

Wildcard Filters

The "wildcard-filters" determine which file types are visible in the file browser. An empty string will default to all files types.

This "magic string" follows the same syntax as . The string comprises pairs of "description" and "file extension(s)", separated by a pipe character ("|"). Multiple file extensions may be listed, separated by semi-colons (";").

Example:

"Text file|*.txt;*.TXT|All files|*.*;*"

In this example we have two pairs:

Text file|*.txt;*.TXT: Description: "Text file" File extension "*.txt" matches: "anything.txt" File extension "*.TXT" matches: "anything.TXT"
All files|*.*;*: Description: "All files" File extension "*.*" matches: "anything.anything" File extension "*" matches: "anything"

Flags

The magic "flags" string is similar to the "Styles" options in . Flags may be an empty string, a single keyword, or a comma separated list of keywords.

Available keywords are:

open : This is a "file open" dialog. Usually this means that the default button's label of the dialog is "Open". Cannot be combined with "save"
save : This is a "file save" dialog. Usually this means that the default button's label of the dialog is "Save". Cannot be combined with "open".
overwrite : For save dialog only: prompt for a confirmation if a file will be overwritten.

Example: Open file dialog for one or more files that must exist.

"open,exists,multiple"

Example: Save file dialog with overwrite prompt if file exists.

"save,overwrite"

Return Values

The File-Button widget attempts to create a valid file path as a string, and assign it to the "variable-name" symbol.

If a single file is selected using the file browser, then the widget text box is updated to show the full path to the selected file.
If multiple files are selected using the file browser (requires "multiple" flag to be set), each file path is enclosed in double quotes. Note: The list of file paths is NOT a LISP list. It is still a string. See example below for how to deal with multiple file paths.
If the file path text box is empty, then the widget variable symbol is set to the default path.

Error Messages

In the event of programming or user errors, the File-Button Widget may return an error message. Understanding these messages can be a great help when debugging a new plug-in.

<Path>is not a valid file path. ****This error occurs if the returned file path is invalid, for example, if the directory does not exist. : This error is most likely to be due to the user manually editing the file path text box with an invalid file path.
Mismatched quotes in <string> ****When the "multiple" flag is set, the file browser returns a list of quoted strings for each path. This error is thrown if the opening quotes do not have matching closing quotes. : This error is most likely to be due to the user manually editing the file path text box and missing one or more quote characters.

Examples

Simple "Open File" Example

;control var "Select file to open" file "" "" "" ""

In this example. only the variable ("var") and the "text-left" ("Select file to open") are explicitly set. Empty strings are passed to the other parameters, so they will all take default values.

In reverse order: the default "flag" is "open", the default wildcard filter is "All files", the default file path is "*default*", the default file name is "untitled", and the default button text is "Select a file".

Simple "Save File" Example

;control var "Select file to save" file "" "" "" "save"

Very much like the simple "open file" example above, except this one is selecting a file for writing.

Advanced "Open File" Example

;control filename "Select file" file "" "*default*/sample-data.txt" "Text file|*.txt;*.TXT|All files|*.*;*" "open,exists"

Unlike the previous examples, all parameters are explicitly defined. The default file name is "sample-data.txt", and by default the file browser filters the file list to show Text files only (ending in ".txt" or ".TXT"). The file browser also has an option to show all files.

Note that the file browser is created by the underlying operating system, so there are subtle differences across platforms. The "exists" flag is only relevant for file browsers that allow you to type the file name. For a purely graphical browser it is not possible to select a file that does not exist.

Note also that the "exists" flag only affects the file browser - it does not prevent the user typing a non-existent file name in the file path text field. If the plugin requires the file to exist, then the plugin code should run a test to ensure that it does. A simple test for the existence of a file, is to try and open it, for example:

Advanced "Save File" Example

In this example, all parameters are explicitly defined:

variable-name: filename
text-left: "Export data to"
button-text: "Select a file"

The provide options in the file browser to show either text files (.txt or .TXT), which is the default, or CSV files (.csv pr .CSV), or HTML files (.html, or .HTML, or .htm, or .HTM), or "All files" (any file name).

Note that on Windows, file extensions are not case sensitive, but Linux, and some Mac computers are case sensitive, so for cross-platform portability it is recommended to use both upper and lower case file name extensions.

Open Multiple Files

;control var "Select one or more files" file "Select" "*default*" "Text file|*.txt;*.TXT|All files|*.*;*" "open,multiple"

In this example, the variable that will be set is var, the default directory is *default*, and the default file type filter is for text files (with an option to show all files). Unlike the previous versions, the file browser may be used to select multiple files (requires Audacity 2.3.1 or later).

If the users selects one or more files using the file browser, then each file path will be enclosed in double quotes. However, the user could type in the path to a single file without quotes, or, as in this case, the default could be an unquoted single file path, so we should check for and support both versions.

To extract all of the the paths from the returned string, we first need to convert it to a more useful form, such as a LISP list:

(setf path-string (format nil "(list ~s )" (string-trim "\"" var)))

Here we have stripped the outer double quotes (if present), and then formatted it into a string that describes a LISP list. So, for example, if the selected files were: "C:\first.txt" and "C:\second.txt", then the value of varwould be ""C:\first.txt""C:\second.txt"", and the value of path-string would be "(list "C:\first.txt" "C:\second.text")".

Important: Note that this is still only a string value, not a LISP list.

To convert this string into a LISP list, we need to evaluate the string as if it were code. Fortunately in Audacity 2.3.1 and later, there is an easy way to do this with the EVAL-STRING function:

(setf paths (eval-string path-string))

paths is now a valid LISP list of strings, which we can iterate through like this:

(dolist (p paths) (print p))

The complete example that can run in the :

Example Applications

These example applications may be run in the , or could be converted to plugins by adding full plugin headers.

These code examples are excessively commented so as to explain what they are doing. For production code, comments should be concise and provide clarification where the intent is not obvious. As far as possible, the code should be self explanatory, but as this is intended for learning purposes, additional explanatory comments are included.

Writing to a File

In this example, we use a File-Button widget to specify a file that will be written to. It is important to note that selecting the file does NOT write to the file, it only captures the file path and file name, which we then write to later in the script. The plugin will get some information about the selected audio, and write (append) it to a file.

First we start with a couple of headers to set the syntax version and plugin type.

;version 4 ;type analyze

Next is our File-Button widget. Note that it has the "save" flag because we are selecting a file to write to.

;control filename "Export to" file "" "data.txt" "Text file|*.txt;*.TXT|All files|*.*;*" "save"

The next three code lines gather the raw information that we will be writing to the file.

When we write to a file with Nyquist, the file is overwritten by the data that we are writing. As we want to append the new data to the file rather than overwriting it, we must first read the existing text from the file and store it in a variable. We can then write the old data, plus the new data back to the file. Here is a function that will read the contents of the file if it exists, and returns the data to the function caller.

As this code is designed to work with text files, we can check that the file name ends with ".txt".

The file name extension is NOT a reliable way to test the file type. In any situation where security is a concern, the file extension must not be relied as an indicator of the file type.

First we assign an empty string as the value of the variable ext.
If the file name is at least 4 characters long, we extract the last 4 characters and assign it as the value of ext.
We can then apply a

So now we can run our main program, which is within a program block.

The program block begins by binding a local variable {{inlineCode|data}}{=mediawiki} to the data returned by the {{inlineCode|read-file}}{=mediawiki} function (defined above).
Then we .

If the file did not end with .txt, we return an error message.

The Complete Code:

Reading Multiple Files

This is an advanced example that uses the File-Button widget to read data from one or more text files. Text handling is not one of Nyquist's strengths (Nyquist is primarily designed for handling audio), hence parsing the text file data is quite complex.

In this example, we will import (read) labels from one or more text files.

For simplicity, we will deal only with the basic label format and not support "spectral" labels.

The data format we will use is compatible with , provided that are NOT used.

For this plug-in, we will specify that the label data file has one label definition per line, and each label definition has a start time (in seconds), and end time (in seconds) and optional label text. The numbers and optional label text may be separated by spaces or tabs. The data should be saved as plain text, with a ".txt" file extension.

Example Data:

The Complete Code:

Filters and EQ

Band-Stop Filter

A band-rejection filter that passes most frequencies unaltered, but stops those in a specific range.

Details

Author: Steve Daulton

A band-rejection filter that passes most frequencies unaltered, but stops those in a specific range.

Parameters:

Center Frequency: 100.0 to 10000.0 [Hz]. Set the 'Center Frequency' slider, or type in a value for the center of the frequency band to block.

Stop-Band Width: 0.250 to 4.000 [Octaves]. Set the Stop-Band Width to determine how wide the cut frequency band will be. Smaller numbers will produce a narrower 'notch' and larger numbers will cut a broader band of frequencies.

This filter uses steep high-pass and low-pass filters to achieve the band-stop effect. The filters iterate to improve the band-stop efficiency for narrow band width and can thereby perform close to total blocking down to almost 1/4 octave.

For even narrower notches a notch filter should be used.

Chebyshev Type I Filter

Type I Chebyshev filters can provide a steeper than but at the expense of more in the .

Details

Author: Kai Fisher

A with options for high-pass or low-pass operation.

Type I Chebyshev filters can provide a steeper than but at the expense of more in the . The plugin provides unity gain (except for ripple) in the passband. This plugin is capable of providing an exceptionally steep cut-off transition by selecting a "high order".

Parameters:

Classic EQ

An Equalizer (EQ) that can modify more than one band at a time.

Details

Authors: Josu Etxeberria and David R.Sky.

An Equalizer (EQ) that can modify more than one band at a time. You have 15 bands to choose from and can manipulate all of of them independently by moving their sliders.

Comb Filter

The name 'comb' filter comes from how it acts on the audio spectrum it's applied to: it looks like a comb with the teeth pointing up.

Details

Author:

The name 'comb' filter comes from how it acts on the audio spectrum it's applied to: it looks like a comb with the teeth pointing up. For example, if you set the comb frequency at 1000 Hz, the comb filter emphasizes 1000 Hz as well as 2000, 3000, 4000 Hz and succeeding frequencies. Produces an 'airy' effect, which is more pronounced the higher the comb decay value is set, and resonance is increasingly produced as well.

A comb filter can be produced using flanger-like settings on a delay effect, but this filter does not use a delay to get the result, so it does sound somewhat different.

Parameters:

Customizable EQ

Customizable single-band equalizer.

Details

Author:

Parameters:

Center frequency: [Hz, 20 - 20000, default 440]

Desk EQ

This equalizer is modelled on the EQ section of the Allen & Heath GL series mixing desk.

Details

Author: Steve Daulton

This EQ is modelled on the EQ section of the Allen & Heath(TM) GL series mixing desk.

It is a 4-band EQ (equaliser) with two semi-parametric mids and provides independent control of four frequency bands plus a low frequency roll-off switch (HPF). Allen & Heath (along with Soundcraft and Neve) are well known for their distinctive "". The two "mid" filters are bell shaped peak/dip filters which affect frequencies around a center point which can be swept from 500 Hz to 15 kHz, and 35 Hz to 1 kHz respectively. The width of the band is selected to provide effective control for both creative and corrective equalisation.

Parameters:

High Pass Filter with Q

A high pass filter with Q, or resonance.

Details

Author:

A high pass filter with Q, or resonance. A high pass filter attenuates frequencies below a given cut-off point. The higher Q is, the more the cut-off frequency will resonate (produce a tone). Applied to white noise, both this filter and the low pass filter with Q can be used to produce wind-like sounds at a constant frequency. See the and low pass filter (LFO) for ability to modulate a fixed resonance cut-off frequency.

Parameters:

High Pass Filter (LFO)

A high pass filter with a low frequency oscillator (LFO).

Details

Author:

A high pass filter with a low frequency oscillator (LFO). A high pass filter attenuates frequencies below a given cut-off point. The LFO in this plugin modulates the cut-off frequency up and down, like on an electronic synthesizer.

Parameters:

High Pass Filter (LFO) - Alternative version

Details

Author:

Parameters:

Center cut-off frequency: [20 to 20000 Hz, default 640]

Hum Remover

A filter for removing the sound of from recordings.

Details

Author: Steve Daulton

A filter for removing the sound of from recordings.

The frequency of mains electricity is 60 Hz in the US, 50 Hz in Europe. This can create electrical interference in recordings with many . To remove the hum, this effect applies a series of notch filters based on the frequencies of mains electricity and the harmonics, which have frequencies that are at exact multiples of that frequency.

To minimize loss of audio data, the number of harmonics may be adjusted so that only as many notches as required to eliminate the audible hum are applied. There are often more odd harmonics than even harmonics, so this effect allows the number of odd and even harmonic filters to be set independently.

The effect can often provide a useful guide as to which frequencies need to be removed.

First, select 50 or 60 Hz with the first control as appropriate, then set the other controls to maximum. Preview the effect frequently while reducing one control at a time to find the minimum settings required to remove the hum.

Low Pass Filter (LFO)

A low pass filter with a low frequency oscillator (LFO).

Details

Author:

A low pass filter with a low frequency oscillator (LFO). A low pass filter attenuates frequencies above a given cut-off point. The LFO in this plugin modulates the cut-off frequency up and down, like on an electronic synthesizer.

Parameters:

Low Pass Filter (LFO) - Alternative version

Details

Author:

Parameters:

Center cut-off frequency: [20 20000 Hz, default 640]

Low Pass Filter with Q

A low pass filter with Q, or resonance.

Details

Author:

A low pass filter with Q, or resonance. A low pass filter attenuates frequencies above a given cut-off point. The higher Q is, the more the cut-off frequency will resonate (produce a tone). Applied to white noise, both this filter and the high pass filter with Q can be used to produce wind-like sounds at a constant frequency. See the and for ability to modulate a fixed resonance cut-off frequency.

Multiband EQ

A multiband equalizer.

Details

Author:

Select total number of bands (T, from 2 to 30), band number (1 to 30, depending on how many total bands T you chose), and apply gain (-24 to +24 db). Determines width of band depending on total band number T you chose.

Mutron

Loosely based on the Mutron stomp box from the late 70's. Basically it is a filter controlled by an envelope follower.

Details

Author: Steven Jones.

Loosely based on the Mutron stomp box from the late 70's. Basically it is a filter controlled by an envelope follower.

Parameters:

Notch Filter

A notch filter cuts out a "notch" in the spectrum of your audio.

Details

Authors: Steve Daulton and Bill Wharrie.

Like its name suggests, a notch filter cuts out a "notch" in the spectrum of your audio. The default frequency (60 Hz) can remove much of the hum that recordings can acquire from 60 Hz mains supply (as used in North and Central America and much of South America). You can set Frequency to 50 Hz to counteract mains hum in other countries. See .

Filter frequencies above 10000 Hz may be entered by typing the value but are only valid up to half of the sample rate of the audio being processed. Q values outside of the slider range can be entered by typing the values but must be greater than 0.01.

Parameters:

Parametric EQ

A parametric equalizer is a variable equalizer effect which provides control of three parameters: amplitude, center frequency and bandwidth.

Details

Author: Steve Daulton and Bill Wharrie

A parametric equalizer is a variable equalizer effect which provides control of three parameters: amplitude, center frequency and bandwidth. This plugin provides control of one frequency band that can be "tuned" to a user defined center frequency. The width of the affected frequency band may be adjusted with the "Width" control and the defined frequency band may be boosted or attenuated according to the "Gain" control.

Parameters:

Random Low Pass Filter

Like someone is playing around with the cut-off frequency knob of your low pass filter.

Details

Author:

Like someone is playing around with the cut-off frequency knob of your low pass filter. Because of the way the random signal is generated, the lower the maximum speed is, the higher the depth factor must be to produce a similar depth of filtering changes. If you generate white noise then apply this effect, you can to some extent simulate constant pitch wind noise.

Parameters:

Resonant Filter

A filter with low pass, high pass and band pass options with a "resonance" control.

Details

Author: Steve Daulton

A filter with low pass, high pass and band pass options with a "resonance" control.

Audio filters are commonly designed to have a smooth frequency response that is essentially flat in the pass band then rolls off to a lower level in the stop band, but in some cases it is desirable to use a filter that has a peak and accentuates frequencies close to the defined filter frequency. Such filters are commonly used in sound synthesis to cause "ringing" at specified frequencies. This tends to be most effective with sounds that have complex frequency content, such as noise.

Parameters:

Shelf Filter

A shelf filter with options for high shelf, low shelf or mid-band.

Details

Author: Steve Daulton

A shelf filter with options for high shelf, low shelf or mid-band.

Low-shelf filter passes all frequencies, but increases or reduces frequencies below the shelf frequency by specified amount. High-shelf filter passes all frequencies, but increases or reduces frequencies above the shelf frequency by specified amount. Mid-band shelf filter passes all frequencies, but increases or reduces frequencies between the low and high cut-off frequencies by specified amount.

Parameters:

Ten Band EQ

An Equalizer (EQ) that can modify one band at a time.

Details

Author:

An Equalizer (EQ) that can modify one band at a time. Select the band number (1 to 10) and gain (-24 to +24 dB).

Vocal reduction and isolation

Warning: This effect can cause data loss on macOS. See for details.

This is the vocal reduction and isolation effect that was included in Audacity prior version 3.5.

Details

Vocal Reduction and Isolation attempts to remove or isolate center-panned audio from a stereo track. Vocals are sometimes (but not always) recorded in this way. The simplest and quickest removal method subtracts one channel from the other, but the result will be (dual) mono. This method is available at "Remove Center Classic: (Mono)" under Action. All other "Remove" options in this effect preserve the stereo image.

The Isolate options all return (dual) mono output. The narrowness of the center slice can be adjusted with the "Strength" slider. Center isolation is not possible using the classic subtraction method.

The Analyze option displays the amount of correlation between the stereo channels and the degree of likelihood that center removal or isolation will work effectively.

Headers Reference

Plugin Headers are specially formatted code comments placed at the top of a Nyquist plugin script.

Any line beginning with a semi-colon (";") is entirely ignored by Nyquist, but properly formatted "header" comments provide instructions that tell Audacity how to create the plugin.

Plugin header format

Plugin headers are written as:

where keyword is the header command, and args is a list of values. For most header commands there must be the correct number of arguments.

Important:

Nyquist plugin headers normally begin with one single semicolon at the beginning of each line.
Headers must be all lower-case except for quoted text (for example: "name") which may include upper-case characters.
Malformed plugin headers are ignored (treated as normal code comments).

Locale Support

Translated headers begin with a dollar character ("$") rather than a semi-colon. The string to be translated is double quoted, and appears between (_ and ).

Multi-language support for a plugin's is available only to plugins that are shipped with Audacity, as the translations must be compiled into Audacity's language files.

Header Syntax

All plugin headers have the syntax: ;keyword args, where args are the parameters ("arguments") for the header command.

Required plugin headers

nyquist plug-in

Tells Audacity "this is a Nyquist plugin". This should normally be the first line as it defines the contents of the file.

name

Name of the plugin as it will appear in the Audacity menu:

Note that for plugins to be used in , the colon character ":" cannot be used (as it is a special character in the Chain text file).

If the plugin has an interface, the name should end with three dots so as to indicate that additional user action is required before the plugin is applied. Plugins that act immediately without additional user action should not have dots at the end of the name.

type

Only one ";type" line should be used.

A plugin cannot appear in several Audacity menus at the same time, but it is possible to write several plugins with the same name and different ";type" lines. Each plugin will then appear in the appropriate menu. Using the same name for more than one plugin is not recommended and should generally be avoided.

Type header

Features

Typical Role

Tool type plugins are typically or plugins that don't fit well in any of the first three roles. They may also be combined with one of the other types:

Type header

Features

version

Use only one ";version" line.

All new plugins should use the most recent version number so that all current features are available. The version line is required to allow Audacity to run the plugin correctly and prevents plugins with new features from being loaded in an old Audacity program that is missing required features.

Version header

Features

Display headers

author

Name of the plugin Author. If this line is added, its text will appear in the Audacity Effect Menu when sorted or grouped by "Publisher". The author name string must be quoted.

copyright

A short statement of the copyright/license terms. For plugins shipped with Audacity, this must be compatible with Audacity's GPL v2 license. The copyright string must be quoted.

Recommended text for GPL v2 license:

;copyright "Released under terms of the GNU General Public License version 2 or later"

Additional copyright details may be included in the plugin code comments, but must not conflict with the terms declared in the copyright header.

release

Displays a release version number for the plugin in the menu.

Plugins that are shipped with Audacity have a release version number equivalent to the Audacity version at the time that the plugin was last updated.

Plugin authors may choose whichever they prefer, but should ensure that later versions of the plugin always have a later version number. If the version number has spaces, it must be enclosed in double quotes.

Any one of the following are valid (though there should be only ONE release header in a plugin):

release 1 release 0.0.1 release "1.0" release "3.5 beta"

Functional headers

codetype

Declaration of code syntax. May be either lisp or sal (lower case).

For LISP syntax plugins this is usually omitted, but it should always be included for SAL syntax plugins.
If the code type is not declared in the , Audacity attempts to deduce the correct syntax from the code.
The code type can only be Lisp syntax or SAL. It cannot be a mix of both.

debugbutton

Show or hide the Debug button. The default is to show the button, but for plugins that are shipped with Audacity, or other plugins that are believed to be bug free, the Debug button may be hidden by setting this to "false" or "disabled"

debugflags

debugflags header

Description

These flags may be used in conjunction with the header to provide a variety of behaviors.

debugbutton true, debugflags trace: Debug window opens if debug button pressed or if Nyquist printed to the debug window.
debugbutton false, debugflags trace: Debug button disabled, but debug window opens if Nyquist printed to the debug window.
debugbutton true, debugflags notrace: Debug window opens only when Debug button is pressed. If Debug button has NOT been pressed, any error messages that arise are routed to the .

helpfile

A may be added to the plugin by giving the relative path and name of a help file. As the button can only be created if the plugin has a GUI, this header should not be used in plugins that do not have a GUI.

The file path is relative to the plugin search path. Normally the help file would be placed in the same location as the plugin when it is installed. To support HTML files with images and/or media, the help file and its resources may be in a folder, and the folder included in the file path. For example, if the help file is called "my_effect.html" and it includes images, then the html file and images may be placed in a folder called "my_effect_help", and the helpfile header would be:

If the help file is not found, the ? button will not appear.

manpage

This is primarily intended for use by plugins that are shipped with Audacity. It is similar to the header, except that it looks for the help file in the search path for Audacity's manual. As with ";helpfile" it should only be used in plugins that have a GUI. For more information, see

maxlen

Specifies the maximum number of samples to be processed in "process" or "analyze" type plugins. This can help the progress bar if length that will be processed is determined by the plugin rather than by the length of selection. It could also be used as a fail-safe for plugins that are specifically designed for short selections. This example limits the number of samples to 1 million:

When the MAXLEN header is used, the Nyquist global variable LEN is the maximum of "length of selection in samples" and "value set by MAXLEN".

In "process" type effects, this may cause the selected audio to be truncated to the specified number of samples. In such cases it may be best to throw an error if "maxlen" is exceeded, for example:

mergeclips

Allows Nyquist plugins to override Audacity's default "clip merge" behaviour. By default, when effects (including generator effects) are applied across one or more clip boundaries and the returned audio is a different length from the original selection, Audacity will add "split lines" at the ends of the returned audio. In all other cases, the returned audio is "merged" into the current audio.

This option only applies when the plugin is applied across clip boundaries (including across "split lines").

Clip Merge Options

-1 Automatic clip merge behaviour (default)

0 Don't merge clips. Effects that are applied across clip boundaries will not be merged into the existing audio (there will be split lines at the ends of the returned audio) whether the returned audio is the same length as the original selection or not.

1 Always merge clips. The returned audio will always be merged into the existing audio (no split lines added).

preview

Provides options for previewing the effect. Multiple preview options may be defined to achieve the desired behaviour.

Preview Options

enabled (default). Preview is enabled.

true Same as "enabled".

disabled Preview is disabled. If Audacity is unable to provide a meaningful preview, then preview should be disabled. This may be required for effects that affect specific time regions within the selection.

false Same as "disabled".

linear Provides an optimisation for previewing multiple tracks by mixing the selected tracks before applying the Nyquist code. This optimisation is disabled by default.

selection When previewing, the Nyquist code is applied to the entire selection (not just the length that will be previewed). Audacity's "Preview" then plays the first few seconds of the processed audio. This may be required for effects that vary over the duration of the selection.

restoresplits

Allows Nyquist plugins to override Audacity's default "split restore" behaviour. By default, when effects (including generator effects) are applied across one or more clip boundaries, Audacity will restore "split lines" at the position of the original clip boundaries.

This option only applies when the plugin is applied across clip boundaries (including across "split lines").

Restore Splits Options

1 Splits at clip boundaries are restored (default)

0 Splits at clip boundaries are not restored (clips are joined).

Note: Nyquist plugins are not currently able to distinguish between silence and "empty space" within the selection, so gaps between audio clips will be treated as if the empty space is an additional "silent" audio clip.

Obsolete plugin headers

These headers are obsolete and no longer used by Audacity. They should not be used in new plugins.

They may still be found in some old plugins, but are now treated by Audacity as ordinary "comments" and simply disregarded.

action

Description shown in progress window.

info

A single line of text to be displayed at the top border of the plugin window. For multiple lines of text, a two-character sequence "\n" may be used within "text" to create a line break.

Control headers

If the plugin includes at least one properly formed "Control" header, Audacity will launch the plugin with a GUI.

Each valid "Control" header adds a widget to the GUI. If there are no "Control" headers, Audacity will attempt to run the effect without a GUI.

There can be several "control" lines in the plugin header. Add one for each widget to appear in the dialog box. The ;control headers should normally be the final headers as they define variables used by the Nyquist code.

Plugin Reference

This page offers a detailed look at the structure and syntax of Nyquist Plugins. It is intended for people who wish to write their own plugins.

If you are looking for extra Nyquist plugins to use, see Nyquist Plugins.
If you are especially interested in Nyquist in Audacity, we highly recommend subscribing to our Audacity forum, which has a section specifically for matters relating to Nyquist.

Overview

Nyquist is a superset of the XLISP programming language, (a dialect of LISP and supports both a LISP syntax and an alternative syntax called SAL. A general introduction to Nyquist is given on the main Nyquist page.

The Audacity Nyquist Interface is implemented in the following files in the Audacity source code:

audacity/src/effects/nyquist/Nyquist.cpp
audacity/lib-src/libnyquist/nyx.c

Nyquist is in many ways a separate program from Audacity (and is also available as a ). Nyquist is embedded in Audacity as a software that may be called from the main Audacity application to provide additional functionality, most notably as "plugins".

When a Nyquist plugin is selected from one of Audacity's menus, Audacity locates the plugin script (the ".NY" file), starts a Nyquist session and passes the Nyquist code to be interpreted by the Nyquist library. Nyquist then attempts to run the program. The result of running the Nyquist script is returned to Audacity.

Nyquist Plugin Header

As in most other computer languages, Nyquist supports code comments. Any line beginning with a semi-colon (;) is entirely ignored by Nyquist. Comments may also be placed at the end of a line of code by beginning the comment with a semi-colon. Nyquist ignores everything from the semi-colon to the end of the line.

In Audacity, special comments are used in Nyquist plugins to pass information to Audacity. As with other code comments, these are ignored entirely by Nyquist, but provide instructions to tell Audacity how to create the plugin.

Plugin Header Example

In this example (derived from the effect), the first four lines make up the essential headers that are required in all Nyquist plugins.

;nyquist plug-in This header tells Audacity that this file is a Nyquist plugin.
;version 4 This header specifies that this is a "4th generation" plugin.
;type process

The other headers enable various options and properties, including the plugin's controls.

Full descriptions of all plugin headers are provide on the page.

Nyquist Plugin Widgets

Nyquist plugins support a range of "widgets", which are control elements for a graphical user interface (GUI). These elements are unique to Nyquist in Audacity.

The GUI is created by Audacity when a plugin contains one or more widget header commands.

As with other plugin headers, they begin with a semicolon (;) and are ignored by Nyquist, except that the variable name of the widget is initialized with a value and made available to Nyquist. This means that Nyquist can access the value that has been set in the widget as the value of the variable specified in the widget header.

Note: The "Text widget" is an exception to the above at it is for display purposes only and does not set a value.

Each widget begins with ";control", and is followed by a number of parameters, one of which defines the type of widget. There are currently nine widget types, though not all of them are available for old versions of Audacity.

When a plugin is launched, Audacity searches the plugin .NY file for valid headers. Every ";control" line that is found gets parsed by Audacity into several tokens, where each token is separated by spaces. If the tokens match one of the defined patterns, then Audacity adds the widget to the GUI, otherwise they are ignored.

Syntax for widgets

;control

var-name

text-left

widget-type

text-right

initial-value

minimum

maximum

Note: "real" (deprecated) is an alternative name for "float" and is provided as legacy support for old plugins. It should not be used in new code.

Italic words in the table denote data types. Because tokens are separated by whitepace, strings containing whitespace must be written within quotation marks.

Note: Older versions of Audacity may not support all of these controls, which may lead to an "unbound symbol" error. Plugin users are encouraged to use the current version of Audacity, to ensure that they can benefit from all of the latest features.

The following code may be run in the of Audacity 2.3.1 or later, and produces the GUI shown above:

The detailed syntax for each widget type is described on the Nyquist Plugins Widgets page.

Tracks and Selections

Audacity passes information about the current Audacity session to the Nyquist interpreter, along with the Nyquist code. Typically, when the code runs, it acts on data that has been passed from Audacity, which often includes the selected audio data, and returns data back to Audacity. Here we shall look at the ways that audio data is passed from Audacity to Nyquist, and from Nyquist back to Audacity.

Passing Selected Audio to Nyquist

For process and analyze type plugins, Nyquist runs the plugin code on each selected track in turn. The audio data is passed from Audacity to Nyquist as a variable called *TRACK* (the asterisks are part of the name).

For mono tracks, the value of *TRACK* is a "sound" (which is a Nyquist ).
For stereo tracks, the value of *TRACK* is an "array". An array is a special kind of ordered list. The array has two elements, both of which are "sounds". The first element holds audio data from the left channel, and the second element hold data from the right channel.

The selected audio is only available to "process" and "analyze" type plugins (including the compound types "tool process" and "tool analyze").

Time and Durations

The way that time and durations are handled depends on the type of plugin.

For process and analyze type plugins, the start time of the selection is seen as "time = 0", and the length of the selection is seen as one unit of time. The absolute length of the sound in seconds can be computed one of the following ways:

NOTE: get-duration answers the question: "If a behavior has a nominal duration of 1, how long will it be after warping it according to the Nyquist environment?" Since many built-in behaviors like OSC and LFO have nominal durations of 1, In process effects, Audacity sets up the environment (including warp) to stretch them by the selection's duration. Otherwise, if you wrote (OSC C4), the result would have a duration of one second instead of the duration of the selection.

In 'generate' effects, this does not happen, so the length specified by the effect is the length that is produced. For example, if you write (OSC C4 3.5), a generate type effect will produce a tone of duration 3.5 seconds.

For generate type plugins, the length of the selection (if there is a selection) is usually ignored by Nyquist. However, if for some reason the length of the selection needs to be known, then *SELECTION* START and END properties may be used (version 4 plugins or later).

When generating sounds with a 'generate' type plugin, durations in Nyquist represent seconds. For example, to generate a 2.5 second sine tone, you could write:

but if the same code is used in a 'process' type plugin, the generated tone will be 2.5 x the duration of the track selection:

If a duration in seconds is required in a 'process' type plugin, this may be done using the command:

The above examples may be run in the .

Global Variables and Reserved Variable Names

In addition to the standard global variables defined in the , Nyquist in Audacity also has global variables that relate specifically to Audacity. Listed here are a few common standard Nyquist globals, and global variables that are relevant to Nyquist in Audacity.

: [float] The sample frequency of the control signals (such as those created by . By default 1/20 of the sample rate of the track.
*DECIMAL-SEPARATOR* : [char] A comma character (#\') or dot character (#\.) depending on the language selected in .
*FILE-SEPARATOR* : [char] The character that separates directories in a path, e.g. "/" (#\/) for Unix, ":" (#\:) for Mac, and "\" (#\\) for Win32.

Other global variables provided by Nyquist can be found in the .

Global Property Lists

Property lists are defined for the global variables *AUDACITY*, *PROJECT*, *SELECTION*, *SYSTEM-DIR*, *SYSTEM-TIME*, and *TRACK*.

For examples using property lists, see the .

AUDACITY

This property list was added in Audacity version 2.1.0

Value: Unbound (not defined).

LANGUAGE : [string] The country code for the language set in . Example - when Audacity's locale setting is for English, (print (get '*audacity* 'language))will print en.
VERSION : [integer list] A list in the form (Audacity_version Audacity_release Audacity_revision) Example: Print the full Audacity version for Audacity 2.1.3 (let ((version-list (get '*audacity*' version))) (format nil "Audacity version ~a.~a.~a" (first version-list)(second version-list)(third version-list)))

PROJECT

Value: Unbound (not defined).

LABELTRACKS : [integer] The number of label tracks in the project.
MIDITRACKS : [integer] The number of note tracks in the project.
NAME : [string] The name of the current project. A project that has not been named (not yet saved) returns an empty string.

SELECTION

Value: Unbound (not defined).

BANDWIDTH : [float] The bandwidth of the frequency selection in octaves (Spectrogram or Spectrogram (log f) track view).
CENTER-HZ : [float] The centre frequency selection in Hz (Spectrogram or Spectrogram (log f) track view).
CHANNELS : [integer] The number of selected audio channels.

SYSTEM-DIR

Value: Unbound (not defined).

BASE : [string] The Audacity installation directory.
DATA : [string] The Audacity data directory. This is where the audacity.cfg, pluginregistry.cfg and EQCurves.xml files are located.
DOCUMENTS [string] The system default documents directory.

SYSTEM-TIME

This property list was added in Audacity version 2.1.1.

Value: A list in the form '(year, day, hours, minutes, seconds), where each list item is an integer.

Example: 5 minutes past 2pm January 1st 2022 would be the list: 2022, 1, 14, 5, 0.

Note that "day" is a number in the range 1 to 366, counted from the start of the year.

This is the time that the Nyquist code is parsed, NOT the time it is executed. It cannot therefore be used for timing events that occur while the code is running. Possible uses for *SYSTEM-TIME* could include automatic naming of files written to disk, or for "" random processes.

DATE : [string] The date formatted according to the current locale. Example: "dd/mm/yy".
DAY : [integer] Day of the month.
DAY-NAME : [string] The name of the day (Example: "Monday").

TRACK

Value: The sound from a selected mono audio track, or an array of two sounds from a selected stereo track (see the Nyquist Stereo Track Tutorial).

Properties of *TRACK* all relate to the track that is being processed. Currently Nyquist only processes audio tracks. When multiple tracks are selected, Nyquist processes each audio track in turn (top to bottom).

CHANNELS : [integer] The number of channels in the track (mono = 1, stereo = 2).
CLIPS : [list or array] For mono tracks, a list of start and end time of each audio clip. For stereo tracks, an array containing a list of clips for each channel. Due to a limitation in Nyquist, the "clips" property can hold a maximum of 1000 start / end times. If an audio channel contains more than 1000 clips, the first 1000 will be listed, and the 1001th item will be NIL. See for an alternative way to get clip times that will work with 1000's of clips.

The VIEW property may change in future versions of Audacity, so is not recommended for public release plugins. During Preview, audio tracks are copied to temporary tracks which are not visible, so the returned "VIEW" value is NIL.

Return Values

Nyquist supports many "data types", including "numbers" (integer or floating-point), "characters" (such as the letter "A", the number "4", or any other ), "strings" (text), "" (a list of data), "" (special kind of indexed list), and "sounds" (a sound / digital signal).

The result of the last computation within the plugin code will be given back from Nyquist to Audacity. According to the data type of the returned value one of the following actions will be invoked in Audacity:

Mono Sound

If a "sound" is returned, the sound will be re-inserted into the selected part of the Audacity track, (or a new track for "generate" type plugins). If the returned sound is shorter or longer than the original sound, the selection will be reduced or augmented. If a mono sound is returned to a stereo track, the same mono sound will be inserted into both channels of the stereo track.

Multi-Channel / Stereo Sound

Nyquist handles multi-channel sounds as an array of sounds. The first element of the array is the left channel, and the second element is the right channel. Audacity currently supports a maximum of two channels in a track (stereo).

Returning an array of sounds to a mono track is an error.To return a stereo sound without error, a stereo track must be selected before running the Nyquist code.

For more information about stereo tracks, see the .

String / Text

When the return value is a character or string, a dialog window will appear with the data displayed as text.

Number

A dialog window will appear with the number displayed as text.

Labels

If an appropriately formatted list is returned to Audacity, a label track will be created below the audio track(s).

For point labels the format is:

((number ``"string") (number ``"string") ... )

The list to create a label track must contain one or more lists, each of which must have:

number - (an integer or float) is the time in seconds from the beginning of the Audacity selection, where the label will appear.
"string" - a string to be displayed in the label's text field.

For region labels, each label list must contain two int-or-float elements, one for the start and one for the end of the label region.

((number````number ``"string") (number````number ``"string") ... )

Audacity will always place returned audio or labels relative to the start of the and not the start of the .

Empty String

An empty string may be used as a "null return", which means that the plugin returns nothing, and no error. An example use would be if you wish to process only the first selected track.

Playing sounds with Nyquist

When using the or (most) Nyquist plugins that have a , if the plugin returns a sound, it may be previewed using the Preview button. In addition to this, it is also possible to play sounds directly from Nyquist, using the function. The PLAY function will be executed when the plugin code runs.

The PLAY function is described in the . The information here describes aspects that are specific to Nyquist in Audacity.

Note that the Nyquist PLAY command does not use Audacity's . Nyquist uses the system default device for playback, and has a default buffer of 100 ms. The buffer setting may be changed with the command. The actual latency values are dependent on the computer sound system and may differ from those requested by Nyquist.

To see the list of available devices when Nyquist plays, set *snd-list-device* to "true" before the play command, then use Debug button to see the output.

(setf *snd-list-devices* t) (play *track*)

To select a specific output device, set *snd-device* to the index number of the device you wish to use (not all devices are valid). For example, if ALSA hw(0,0) is device 0, select it with:

(setf *snd-device* 0) (setf *snd-list-devices* t) (play *track*)

It is not possible to interrupt Nyquist playback. The sound will continue playing until it reaches the end, and other Audacity functions are disabled until Nyquist playback has finished.

To limit the amount of audio that will play, the length of the sound must be defined before starting playback. For example, to play the first 1 second of a selection, you could write (LISP syntax):

Note also that if a plugin uses Nyquist PLAY command, using Previewwill cause an error on some machines because Audacity may not be able to access the audio device while it is being used by Nyquist. For "own use" plugins, if you have more than one sound card, a possible workaround to enable Preview and Nyquist PLAY simultaneously, is to set the Nyquist playback device to a different device to that which Audacity uses. For public release plugins the Preview button should normally be disabled if Nyquist PLAY is used.

Plugin Translations

Nyquist plugins provide two mechanisms for translation into the language specified in Audacity's preferences.

One method is exclusively for plugins that are shipped by default with Audacity and requires compiling Audacity from source, plus several other steps involving . Unfortunately this method is not documented, so only a brief description is provided here.

The other method may be used by plugin developers for their "third party" plugins, but can be used only for returned strings and not for the main plugin interface.

Translation for shipped effects

Header comments in translated plugins begin with a dollar "$" character rather than the usual semicolon ";" character. The strings to be translated are then wrapped in a function that has a one character name "_" (underscore).

Example: In the effect, the header is changed from:

;name "Adjustable Fade"

to:

$name (_ "Adjustable Fade")

;control lines become $control. As with other translated headers, the $ symbol replaces the normal semicolon. The line is ignored by Nyquist as a comment, but is visible to Audacity for translation and for creating a .

The options in Multiple-choice widgets may be translated. For example:

;control var (_ "Translated left text") choice ((_ "Yes") (_ "No")) 0

The above example is not safe to use. See the "Limitations" section below.

Macros and portability: To allow portability of settings and macros, choices may include a non-translated form of each choice. The non-translated form is used by Macros but is not normally visible to users.

;control var (_ "Translated left text") choice (("Label1" (_ "Translated Label 1")) ("Label2" (_ "Translated Label 2"))) 0

Other user visible strings: Other strings that are visible to users are marked for translation using the "underscore" function. An example from the Adjustable Fade plugin:

(format nil (_ "~aPercentage values cannot be negative.") err)

Limitations

Control characters like (new line), (tab) are not supported. The workaround is to use Lisp format directives instead:

Bad (does not work correctly):

(print (_ "Line one.\nLine two."))

Good:

(print (format nil (_ "Line one.~%Line two.")))

Note that translations may contain Unicode characters that are not supported by Nyquist. It is therefore important that any translated strings that need to be machine readable (such as Multiple-Choice widget options) should also have a non-translated form.

;control var (_ "Translated left text") choice (("Label1" (_ "Translated Label 1")) ("Label2" (_ "Translated Label 2"))) 0

Translation for third party effects

It is not currently possible to provide translations for a third party plugin's main interface, unless the name is the same as a translated Nyquist plugin that is already shipped with Audacity. It is highly recommended to NOT reuse the same name as a shipped plugin for a third party plugin.

Translations may be provided for return value messages and debug messages. To do this, the string must be marked for translation by wrapping it in the "underscore" function. The translation must also be provided in a specially formatted list variable *locale*.

The format for the *locale* list is: (LIST (language-list) [(language-list) ...])

where "language-list" is a list in the form: (LIST country-code (translations))

and the "translations" are list in the form: (LIST (List "string" "translation") [(List "string" "translation")...])

The *locale* list may contain any number of "language-list" elements, where each language-list is a list of two strings.
The first element of each "language-list" is the country code (for example "en" or "fr"),
The second item of each "language-list" is a list of translation pairs.

A working example may be found in the .

Scripting reference

This page lists scripting commands.

Yes these are the same commands as in the menus, same as in "Commands and Shortcuts" too, just presented differently.

Presented in a format useful to people using:
- Macros or
- Python Scripting or
- AUD-DO.
Most of this page is automatically generated.

A few commands are intentionally omitted from the Macro Manager (such as "Close:") because they are unsuitable for use in Macros.

This table shows the items in the menus that are scriptable.

The Scripting Ids, parameters and defaults are all likely to change between versions.
Boolean values must be given as 1 (true) or 0 (false).

The File Menu provides commands for creating, opening and saving Audacity projects and importing and exporting audio files

Scripting Id

Action

Parameters

Description

File: Save Project

Various ways to save a project.

Scripting Id

Action

Parameters

Description

File: Export

For exporting audio files

Scripting Id

Action

Parameters

Description

File: Import

For importing audio files or label files into your project

Scripting Id

Action

Parameters

Description

The Edit Menu provides standard edit commands (Undo, Redo, Cut, Copy, Paste and Delete) plus many other commands specific to editing audio or labels

Scripting Id

Action

Parameters

Description

Edit: Remove Special

For more "advanced" removal of audio

Scripting Id

Action

Parameters

Description

Edit: Clip Boundaries

Create or remove separate clips in the audio track. A clip inside an audio track is a separate section of that track which has been split so that it can be manipulated somewhat independently of the other clips in the track.

Scripting Id

Action

Parameters

Description

Edit: Labels

These commands are to add and edit labels.

Scripting Id

Action

Parameters

Description

Edit: Labeled Audio

Labeled Audio commands apply standard Edit Menu commands to the audio of one or more regions that are labeled. The labels themselves are not affected.

Scripting Id

Action

Parameters

Description

Select Menu has commands that enable you make selections of tracks or parts of the tracks in your project.

Scripting Id

Action

Parameters

Description

Select: Tracks

Tracks

Scripting Id

Action

Parameters

Description

Select: Region

For modifying, saving and restoring a selection.

Scripting Id

Action

Parameters

Description

Select: Spectral

For making a selection of a frequency range.

Scripting Id

Action

Parameters

Description

Select: Clip Boundaries

For modifying a selection, taking account of clips.

Scripting Id

Action

Parameters

Description

View Menu has commands that determine the amount of detail you see in all the tracks in the project window. It also lets you show or hide Toolbars and some additional windows such as Undo History.

Scripting Id

Action

Parameters

Description

View: Zoom

Zoom in/out on the horizontal axis. Show more detail or show a longer length of time.

Scripting Id

Action

Parameters

Description

View: Track Size

Controls the sizes of tracks.

Scripting Id

Action

Parameters

Description

Move forward/backwards through the audio

Scripting Id

Action

Parameters

Description

View: Toolbars

Toolbars can be used to determine which of the Audacity toolbars are displayed. By default all toolbars are shown except Spectral Selection and Scrub

Scripting Id

Action

Parameters

Description

Transport Menu commands let you play or stop, loop play, scrub play or record (including timed and sound activated recordings).

Scripting Id

Action

Parameters

Description

Transport: Playing

These commands control playback in Audacity. You can Start, Stop or Pause playback of the audio in your project.

Scripting Id

Action

Parameters

Description

Transport: Recording

These commands control recording in Audacity. You can Start, Stop or Pause recording in your project. You can either start a recording on your existing track or on a new track.

Scripting Id

Action

Parameters

Description

Transport: Scrubbing

Scrubbing is the action of moving the mouse pointer right or left so as to adjust the position, speed or direction of playback, listening to the audio at the same time - a convenient way to quickly navigate the waveform to find a particular event of interest. Speed changes are made by rotating the mouse wheel while scrubbing.

Scripting Id

Action

Parameters

Description

Transport: Cursor to

These commands let you move the cursor to the start or end of the selection, track or any adjacent Clip that you may have

Scripting Id

Action

Parameters

Description

Transport: Transport Options

This submenu lets you manage and set various options for transport (playing and recording) in Audacity

Scripting Id

Action

Parameters

Description

Tracks Menu provides commands for creating and removing tracks, applying operations to selected tracks such as mixing, resampling or converting from stereo to mono, and lets you add or edit labels.

Scripting Id

Action

Parameters

Description

Tracks: Add New

Adds a new track

Scripting Id

Action

Parameters

Description

Tracks: Mix

Mixes down selected tracks to mono or stereo tracks

Scripting Id

Action

Parameters

Description

Tracks: Mute/Unmute

Mutes or unmutes audio tracks in the project

Scripting Id

Action

Parameters

Description

Tracks: Pan

Pans left right or center audio tracks in the project

Scripting Id

Action

Parameters

Description

Tracks: Align Tracks

Commands that provide an automatic way of aligning selected tracks with the cursor, the selection, or with the start of the project.

Scripting Id

Action

Parameters

Description

Tracks: Sort Tracks

Sorts all tracks in the project from top to bottom in the project window, by Start Time or by Name.

Scripting Id

Action

Parameters

Description

Generate Menu lets you create audio containing tones, noise or silence.

Scripting Id

Action

Parameters

Description

Generate: Built-in

Shows the list of available Audacity built-in effects but only if the user has effects "Grouped by Type" in Effects Preferences.

Scripting Id

Action

Parameters

Description

Generate: Nyquist

Shows the list of available Nyquist effects but only if the user has effects "Grouped by Type" in Effects Preferences.

Scripting Id

Action

Parameters

Description

Audacity includes many built-in effects and also lets you use a wide range of plugin effects.

Scripting Id

Action

Parameters

Description

Effect: Built-in

No special notes for Built-in

Scripting Id

Action

Parameters

Description

Effect: Nyquist

No special notes for Nyquist

Scripting Id

Action

Parameters

Description

The Analyze Menu contains tools for finding out about the characteristics of your audio, or labeling key feature.

Scripting Id

Action

Parameters

Description

Analyze: Nyquist

No special notes for Nyquist

Scripting Id

Action

Parameters

Description

The Tools Menu contains customisable tools.

Scripting Id

Action

Parameters

Description

Tools: Apply Macro

Displays a menu with list of all your Macros. Selecting any of these Macros by clicking on it will cause that Macro to be applied to the current project.

Scripting Id

Action

Parameters

Description

The Extra menu provides access to additional Commands that are not available in the normal default Audacity menus.

Scripting Id

Action

Parameters

Description

Extra: Transport

Extra commands related to play and record

Scripting Id

Action

Parameters

Description

Extra: Tools

Extra commands to select the tool, for example time-shift, envelopes, multi-tool.

Scripting Id

Action

Parameters

Description

Extra: Mixer

Extra commands related to volume

Scripting Id

Action

Parameters

Description

Extra: Mixer

Extra commands related to editing

Scripting Id

Action

Parameters

Description

Extra: Play-at-Speed

Extra commands related to play at speed

Scripting Id

Action

Parameters

Description

Extra: Seek

Extra commands related to seeking

Scripting Id

Action

Parameters

Description

Extra: Device

Extra commands related to selecting a device

Scripting Id

Action

Parameters

Description

Extra: Selection

Extra commands related to selecting.

Scripting Id

Action

Parameters

Description

Extra: Focus

Extra commands to set focus, usually focus on one track

Scripting Id

Action

Parameters

Description

Extra: Cursor

Extra commands to move the cursor

Scripting Id

Action

Parameters

Description

Extra: Track

Extra commands to operate on a track that has focus

Scripting Id

Action

Parameters

Description

Extra: Scriptables I

These commands were originally written for scripting Audacity, e.g via a Python script that uses mod-script-pipe. The commands though are also present in the menu, available from macros, and available from within Nyquist using (AUD-DO "command")

Scripting Id

Action

Parameters

Description

Extra: Scriptables II

Like Scriptables I, but these ones are less commonly used from the menu.

Scripting Id

Action

Parameters

Description

The Help Menu lets you find out more about the Audacity application and how to use it. It also includes some diagnostic tools.

Scripting Id

Action

Parameters

Description

Help: Diagnostics

A set of diagnostic tools

Scripting Id

Action

Parameters

Description

These are additional commands that do not appear in any menu

Scripting Id

Action

Parameters

Description

Playback equalization for 78 rpm shellacs and early 33⅓ LPs

The audio on almost every phonograph record is not the same as that originally performed. For technical reasons the signal's frequencies need to be modified when cutting the disc. Playback equalization (EQ or de-emphasis) is necessary to restore the signal's original frequencies. Only thus can music lovers enjoy the original sound of the music performed long ago from their rare discs.

Usage

The most relevant EQ curves are presented as Table 1:

You can download some of them from the section of this page, and import them into Audacity using or
You can generate any curve yourself with the plugin
You can set the sliders of any digital or analog graphic equalizer manually
You can determine appropriate settings for any adjustable analog pre-amplifier.

Which EQ curve will be needed for a specific record label is answered:

for 78 rpm shellacs in
for early LPs in

Using EQ curves in Audacity

Once , you can import the curve in the Filter Curve EQ or Graphic EQ effects, by clicking Presets & settings -> Import....

Equalization (EQ) Curves explained

When phonograph records are made, the sound being recorded is deliberately distorted by reducing the volume of the low frequencies and increasing the volume of the high frequencies. This process, known as 'pre-emphasis', allows the low frequencies to be accommodated in the limitations of the record groove and reduces the effect of high frequency surface noise. If pre-emphasis was not carried out, the bass notes in the music would create a groove in the record that oscillated so wildly that the stylus could jump out of it on playback, and the treble notes would be drowned out by the surface noise of the stylus in the groove.

On playback, the pre-emphasis must be reversed in order to restore the original sound. This is known as 'de-emphasis' or equalization (EQ).

Modern vinyl records use a method of pre-emphasis and de-emphasis adopted by the Recording Industry Association of America (RIAA) in the 1950's, and the EQ curve used is known as the RIAA curve. However, before the RIAA curve was adopted, each record label used its own EQ curve for recording and, for these records (78rpm and early vinyl), the correct EQ curve must be used for playback.

Each EQ curve is a combination of two filter characteristics; a bass boost curve, defined by a 'Bass Turnover' (or 3dB) frequency, and a treble cut curve, defined by a '10 kHz Gain Roll-off' parameter, i.e. a defined level of treble cut at 10 kHz.

As an example, Figure 1 below shows the characteristic of the bass boost curve defined by a 500Hz Bass Turnover, and Figure 2 shows the characteristic of the treble cut curve defined by a 10 kHz Gain Roll-off of -13.7dB. These two curves, when combined, give the characteristic shown in Figure 3.\

The EQ curve may also include a Low Frequency Shelving filter, (although it is absent from the definition of most 78 rpm EQ curves). This addition reduces the effect of the bass boost at very low frequencies (typically 50 or 100 Hz) in order to attenuate low-frequency noise such as turntable rumble. Figure 4 shows the effect of a 50 Hz LF shelving filter being added to the curve in Figure 3. This is in fact the RIAA standard EQ curve.

Acoustically recorded (pre-electric) 78 rpm records have a completely different characteristic because they were cut with a different type of cutter (For more details see: Acoustic recordings). In some early EQ curves of electrically recorded shellacs, while there is a bass boost curve, there is no treble cut necessary – i.e. the 10 kHz gain roll-off is zero.

Note that in the combined EQ curve, the gains at the Bass Turnover frequency and at 10 kHz may be different from those specified by the parameters. This is not an error, but is due to fact that the gains of the bass boost and treble cut curves are simply added together.

Because 78 rpm EQ curves were non-standard and, in many cases, accurate records were not kept to show what EQ curves were used when recording 78s, there is a degree of uncertainty about what is the correct playback EQ for many record labels. The tables below have been obtained from websites which, in their turn, have compiled data from a number of sources and should prove reasonably accurate. However, the ear of the listener is the final arbiter - if it doesn't sound right, it isn't right!

According to NAB standards, the nominal speed of a 78 rpm record is precisely 78.26 rpm +/- 0.3% (for North America and other countries with an utility frequency of 60 Hz). According to British Standards Institution it is 77.92 rpm +/- 0.5% (for Britain, Europe and other countries with a mains frequency of 50 Hz).

EQ Curves

Pre-equalization of most records – especially of shellacs – was always determined by the cutter head used and often by internal regulations of the record company. Both left quite some room for the recording engineer to make changes to improve the sound. Also if Graumann uses 250 Hz in playback of an EMI disc and Copeland votes for 300 Hz this is not a contradiction. Both mean the same EQ curve but have different opinions on what sounds best. This should encourage you to try both versions and take the one which sounds right to your ears.

Please do not worry about fractions of a dB! Still in the 1960s an accuracy of a curve of +/- 2 dB was considered to be standard. In the 1950s +/- 3 dB were a very fine result and nobody will ever know if recording engineers in the 1940s or 1930s applied their curves correctly (or if they applied them at all!) So the spread in pre-equalization during recording will outnumber any bias in playback equalization by far.

Table of EQ Curves

The most relevant EQ curves are presented in Table 1. All curves are described from the point of view of a playback or de-emphasis curve, where bass / low frequencies must be amplified / boosted and where treble / high frequencies must be attenuated / cut in order to achieve the original sound that had been recorded. The corresponding pre-emphasis curve used for cutting the master disk is inverse.

When comparing with lists provided by the manufacturers of equalizer pre-amps it should be considered that those may be misleading, as they might not quote the correct parameters of the curve but rather the next-best possible settings of these devices. For example the Conductart OWL 1 Sound Restoration Module – a renowned pre-amp of the 1980s – offered settings of flat/ 250/ 375/ 500/ 750/ 1000/ RIAA for turnover and flat/ 5/ 8.5/ 12/ 14/ 16/ RIAA for roll-off. Thus for the widely used standard “AES 400N-12” settings of 375 Hz and -12 dB were listed; for the “Bartok 629C-16” curve it was 750 Hz and -16 dB and for “LONDON LP 500C-10.5” it was 500 Hz and -8.5 dB. These recommendations were quoted or copied by other authors and three “new characteristics” had come to existence.

Table 1 gives the three parameters to characterize any EQ curve: the turnover frequency f1 for bass shelf, f2 for bass boost and f3 for treble cut (or alternatively the three corresponding time constants τ1, τ2 and τ3). These are the necessary conditions to compute and plot any EQ curve, determine the correct settings of a digital equalizer or to solder an electronic filter circuit.

The gain at two typical frequencies will give you a rough impression of what the curve does to the audio from the record. The frequencies are:

50 Hz, where usually the bass shelf becomes effective
10 kHz, because the treble curve is often indicated by roll-off at 10,000 Hz

The very descriptive “code” is a good tool to avoid misunderstanding when EQ curves come under various alias names (what they do too often).

The first 3-digit number indicates the turnover frequency of bass boost (f2)
The letter in the middle is N … (“None”) if no bass shelving is applied, or R … 20 dB (named R after RCA or RIAA) B … 18 dB A … 16 dB C … 14 dB (named C after Columbia LP curve) X … 12 dB
The last number shows the reduction or roll-off of treble at 10 kHz and is always preceded by a minus sign. Please mind that this is only a code and that the exact value – after normalization to 0 dB at 1000 Hz – might be different.

This code can be used to find the correct settings of most equalizer pre-amps.

(Example: “RIAA 500R-13.7” means for the RIAA curve that bass must be boosted below 500 Hz, but no more than + 20 dB and that treble must be cut at 10,000 Hz to – 13.7 dB)

The geographic region and the time period are added to allow a qualified guess for the required EQ should a record label not be listed. In general, American recording curves were more deliberate in cutting bass and boosting treble. The British and Europeans tended to apply only the necessary minimum of bass attenuation and often no treble boost at all, that means they had a “flat” treble curve. Early pre-emphasis curves were simply built and rather soft. In the late years (after 1945) curves became highly sophisticated, with the third turnover frequency f1 added to manage the bass shelving and also with gain ranging from -20 dB to + 20dB.

Table 1: Playback Equalization Curves

Region

Timeperiod

Curve Name, alias names

Time constants

Turnover frequencies

Bass shelf

Bass boost

Treble cut

Citations

Table 1 is mostly based on Tab. 2a of: Heinz O. Graumann, Schallplatten-Schneidkennlinien und ihre Entzerrung, in: FUNKSCHAU 1958 / Heft 15, pp 359 ff* computed frequencies to get 6 or 8 dB @ 10 kHz

[1] CCIR used by Deutsche Grammophon modified with 50 Hz bass shelving => IEC N78 [Brice]

[2] Used by British Decca and for London releases in US and UK, mostly M33. Cf.: Wolfgang Leister, The London Curve, in ARSC Journal, vol.48:2, Fall 2017, p.163

[3] Gary A. Galo, The Columbia LP Equalization Curve, ARSC conference March 2008; Gary A. Galo, Disc Recording Equalization Demystified, in ARSC Journal Fall 1996

78 rpm EQ Curve Generator

EQ Curves for Audacity can be generated from these Frequency and Roll-off values using the experimental Nyquist plugin "78 RPM EQ Curve Generator". This plugin is obtainable from the top of this and requires Audacity 1.3.13 or later. Please give feedback on this plug-in, or ask for help if you need it, by replying to that Forum topic.

Extract 78EQCurveGen.ny from the zip file downloaded from the above Forum topic.
Place 78EQCurveGen.ny in the "Plug-Ins" folder inside the Audacity installation folder, then launch or restart Audacity. For more help installing the .ny file to the correct location, click here.
Click . You can find help inside the plugin by choosing one of the Help options in "Select Function or Help".

EQ Curves Library

Here you can find some useful EQ curves for download to Audacity for use in Effect -> EQ and Filters -> Graphic EQ and Filter Curve EQ. (Curves are in TXT file format, as required in current Audacity and compatible down to version 2.4.0).

78 rpm shellacs

EQ Curve file

Description

pre-RIAA 33⅓ LPs

EQ curve files

Description

Individual fine tuning

In some cases it will be not enough to apply the correct EQ to get the desired result. According to the condition of the record and to personal listening preferences you might consider one of the following methods:

The 250-or-300-Hz dilemma: To use “European250” or “Blumlein300” EQ seems to be not a question of right or wrong but of personal listening preferences. In general, Continental European authors prefer 250 Hz (derived from the original Western Electric recommendation) for Decca (Brit. and Europ.), Brunswick, Cetra, Columbia (Brit.), EMI-HMV and Parlophone. Englishman Copeland favors 300 Hz (derived from the recording characteristic of the Blumlein cutter) for British EMI, His Master’s Voice and Columbia and also for Odeon. Copeland puts it like this: “[…] but when I’m not sure I use 300 Hz.” [Copeland, Manual, p 129]. Being derived from the previous 250-or-300-Hz curve the same applies to “DECCA78” which was used from 1944 for shellacs with the ffrr system. So you should also feel free to decide the 250-or-300-Hz question according to your own listening preference: 300 Hz will give an extra amplification of bass in play back (ca 1.5 dB at 50 Hz).
To remove low frequency noise Robinson (MidiMagic) recommends a low cut filter at 100 Hz with just 6 dB/octave. (Especially for many acoustic recordings which have only noise below 150 Hz or for the “long-playing” shellacs of RCA Victor of 1931/32). This filter will do exactly the same as the “C”-type bass shelf of Columbia LP curve.

Remarks for Analog Purists

Hiss and high frequency scratch due to old worn records: When digitizing such recordings Audacity’s will do a good job to improve the sound once and for all. Those who prefer entirely analog replay with an adjustable pre-amplifier will have the opportunity to improve the sound every time they replay. They can cut / attenuate the frequency range most affected by the noise. A higher value for roll-off at 10 kHz than the “correct” EQ will usually give a better result than a simple treble filter – but: at the expense of the high frequencies of the audio itself.
Dull, lifeless sound: If you improve poor bass on discs of any speed by choosing a higher bass turnover frequency than the “correct” EQ, there will be the welcome side effect of moderately amplifying midrange frequencies. This will bring life to the core octaves of a piece of music by improving instrument and vocal characteristics.

Acoustic recordings and Broadcast Transcription Discs

Acoustic recordings (before 1926) are beyond the scope of this page. In these pioneer years speeds varied from 70 to 90 rpm, groove modulation could be lateral, vertical or diagonal and some records were even cut outward with the audio starting at the center. A special turntable and a range of styli / needles are needed to replay.

All acoustics were recorded without any pre-equalization, simply because a modification of the audio was impossible before electric microphones and amplifiers came into use. Nonetheless there are conflicting opinions as to the result:

According to various authors the acoustical recording process had an "inherent mechanical equalization", which results – within the limited frequency range of approx. 150 to 4000 Hz – in a constant velocity characteristic one would only expect from a magnetic cutter. With a magnetic cartridge this would command to be replayed “flat”. Please note that the acoustical recording characteristic is not equalized at all.

According to Robinson an acoustical recording must have a constant-amplitude characteristic which will be correctly reproduced by playing back with a gramophone needle or a piezoelectric crystal pickup. A magnetic cartridge will – by its constant velocity characteristic – double the amplitude whenever the frequency doubles. To compensate for the magnetic pickup MidiMagic recommends an “800N-16” EQ curve, which comes close to the theoretical characteristic of a constant velocity device. Some more information is here on and on . Please note that the acoustical recording characteristic is not equalized at all.

Kolkowski’s results of a of an acoustic recording session show that bass needs heavy equalization if the losses in the recording horn (here below 400 Hz) shall be compensated for. Parametric equalization may be used at resonant frequencies. Treble should be amplified (!) to compensate for the high-frequency roll-off of the recorder. Due to the individual properties (defects) of recording horns and recorders there will be no “general characteristic” of acoustics and therefore no general EQ.

gives useful information on vintage labels as Edison, Berliner, Pathé or Zonophone and playback EQ recommendations.

Scientific help regarding valuable historic recordings can be found at (International Association of Sound and Audiovisual Archives) and at (Association for Recorded Sound Collections).

Broadcast Transcription Discs are not in the focus of this page either. Those were recordable lacquer discs, mostly 16 inch in diameter, played at 33⅓ or 78 rpm. They were professionally used by radio broadcasters. Some more information is in .

In America many of these discs were recorded under the standard of the National Association of Broadcasters (NAB) of 1942. The very same recording curve had been used by NBC under the name “Orthacoustic” since mid 1930s. This “NAB Transcription (1942)” playback EQ setting can be downloaded here.

The British Broadcasting Corporation (BBC) used a rather exotic curve as a house standard. The version in use after 1949 has been reconstructed from Longford-Smith’s publication of 1952 as an Audacity EQ setting “BBC Transcription (1949)” and can be downloaded here.

78 rpm shellac labels and their EQ

This page is about electrical recordings since 1925 on 78 rpm discs made of shellac! The invention of the Electrical Recording System by Bell Laboratories / Western Electric which was licensed to industry leaders Columbia Records and Victor set some de-facto standards: speed is always 78 rpm, cut is always lateral (same as later mono LPs) and the groove type is always Normal Groove (also named coarse groove). Therefore shellacs are sometimes referred to as N78 (which stands for normal groove discs, played at 78 rpm).

A turntable capable of 78 rpm will be useful. You will need a MONO stylus with 2.5 mil (64 μm), for early electricals possibly one with 3 mil (76 μm) and this Audacity Wiki!

It is assumed that you replay your discs “flat” (without any analog de-equalization) and apply the necessary EQ after digitizing with Audacity . If it is necessary to play the record through a system that applies modern RIAA equalization, select the "RIAA" curve in Audacity's Filter Curve EQ effect and use the Invert button to invert and thus remove the incorrect RIAA equalization before applying the appropriate equalization to the recording.

In case sources did not agree on one EQ curve, their different opinions are listed and you will have to trust your ears.

Table 2: 78 rpm Shellac Labels and Their EQ

Remarks

[Bc] ... Due to changes in the setup of the Blumlein cutter the characteristic of the recordings could vary between 180 Hz-FLAT and 500 Hz-FLAT, resulting in +/- 4 dB at 50 Hz. Copeland suggests 300 Hz as an average value.
[CAP]... used its own “Capitol curve” 400N-12.7. Play back with “AES” 400N-12.3!

Early 33⅓ LP labels and their EQ

After the launch of the “long-playing record 33⅓ rpm” by Columbia in 1948 (which used vinyl discs and a narrower groove width – microgroove records or M33) record producers experimented a lot to fully exploit the potential of the new medium. Bass shelving came into use to limit the necessary bass boost in playback and – as a consequence of the extended frequency range – necessary gain reached values as high as +/- 20 dB. So recording characteristics varied considerably!

The “poor sound quality” of some early LPs is nowadays considered to be mostly a result of the wrong EQ in playback.

Standardization was reached with the “New Orthophonic” curve of RCA which was to become the world standard by the name of RIAA. In America most labels switched to RIAA around 1955 – Europe followed by 1962.

How to identify RIAA recordings:

“ORTHOphonic” or “New Orthophonic” (after August 1952), “NARTB” or “New NARTB” (after June 1953) or “New AES” (after 1954) indicate RIAA equalization.

In case that sources did not agree on one EQ curve, their different opinions are listed and you will have to trust your ears.

Table 3: Early 33⅓ LP Labels And Their EQ

Remarks

[1]... This EQ can be traced back to Langford-Smith (1952), who vaguely describes a “London LP curve (Jan. 1951)”. Powell reads this as 300Hz (wrong!) and -14 dB (correct!). Copeland judges evidence “to be very defective.” No evidence of usage.
[CAP]... used its own “Capitol curve” 400N-12.7. Play back with “AES” 400N-12.3!

Sources, links and reading references

Sources of tables 2 and 3:

AT ... AudacityTeam own research
ES ... and the updated EQ list from the of their re-equalizer pre-amp in which they also have very useful tips how to identify LPs by their matrix number (British London / Decca, American Decca, American Columbia, RCA Victor). Please mind that they quote settings of their device which have to be translated back into parameters of EQ curves.

Recommended analog reference

James R. Powell, Jr. and Randall G. Stehle, "Playback Equalizer Settings for 78 RPM Recordings", Third Edition, Gramophone Adventures, Portage, MI, 1993, 2002, 2007. A compilation of Powell’s subjective recommendations of Owl 1 settings for approx. 1800 discs / 400 labels (mostly American and Jazz). Reprint of 3rd edition available at .
Fritz Langford-Smith, Radiotron Designer's Handbook, Wireless Press, Sydney, Fourth edition, 1952.
James Moir, High Quality Sound Reproduction, Chapman & Hall Ltd., London, 1958

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