# Effect Menu

### From Audacity Manual

Audacity includes many built-in effects and also lets you use a wide range of plug-in effects. You can download many free plug-ins for Audacity from http://audacity.sourceforge.net/download/plugins and the links thereon.

To apply an effect, select part or all of the tracks you want to modify, and select the effect from the menu. Titles which end in an ellipsis (...) will bring up a dialog asking you for more parameters.

Although by default, the only effects shortcut is CTRL + R to repeat the last used effect, it is possible to set up your own shortcut for any effect in the menu. For instructions on how to do this please see Keyboard Preferences.

| When playing, recording or paused, the Effect menu will appear grayed out, because changes to the audio data cannot be made until you press the yellow Stop button .

## Classes of Effect

There are five classes of effects - the built-in Effects, and four classes of plug-in effects which allow you to download and install additional effects. All classes of effect are applied in the same way. The effects classes are:

- Built-in Effects
- Nyquist Effect Plug-ins
- LADSPA Effect Plug-ins
- VST Effect Plug-ins (Windows and Mac only)
- Audio Unit Plug-ins (Mac only)

## List of Built-in Effects

Audacity's built-in effects (those that appear in the program irrespective of the contents of your Audacity and other Plug-ins folders) are above the divider in the Effect menu.

Most of the built-in effects have a "Preview" button. This allows you to listen to how the first three seconds of the selected audio will sound with your effect applied. If it does not sound quite as you want, adjust the controls of the effect and preview again. The preview length can be changed on the Playback tab of Preferences.

### Amplify...

Increases or decreases the volume of the audio you have selected. When you open the dialog, Audacity automatically calculates the maximum amount you could amplify the selected audio without causing clipping (distortion caused by trying to make the audio too loud).

### Auto Duck...

Reduces (ducks) the volume of one or more tracks whenever the volume of a specified "control" track reaches a particular level. Typically used to make a music track softer whenever speech in a commentary track is heard.

### Bass and Treble...

Increases or decreases the lower frequencies and higher frequencies of your audio independently. It behaves just like the bass and treble controls on a domestic stereo system.

### Change Pitch...

Change the pitch of a track without changing its tempo.

### Change Speed...

Change the speed of a track, also changing its pitch.

### Change Tempo...

Change the tempo of a selection without changing its pitch.

### Click Removal...

Click Removal is designed to remove individual clicks on audio tracks and is especially suited to declicking recordings made from vinyl records, without damaging the rest of the audio. It will usually work best on very short clicks. For broader individual pops, you could try the Repair effect.

### Compressor...

Compresses the dynamic range by two alternative methods. The default "RMS" method makes the louder parts softer, but leaves the quieter audio alone. The alternative "peaks" method makes the entire audio louder, but amplifies the louder parts less than the quieter parts. Make-up gain can be applied to either method, making the result as loud as possible without clipping, but not changing the dynamic range further.

### Echo...

Repeats the selected audio again and again, normally softer each time. The delay time between each repeat is fixed, with no pause in between each repeat. For a more configurable echo effect with a variable delay time and pitch-changed echoes, see Delay...

### Equalization...

Adjusts the volume levels of particular frequencies.

### Fade In

Applies a fade-in to the selected audio, so that the amplitude changes gradually from silence at the start of the selection to the original amplitude at the end of the selection. The shape of the fade is linear. The rapidity of the fade-in depends entirely on the length of the selection it is applied to.

### Fade Out

Applies a fade-out to the selected audio, so that the amplitude changes gradually from the original amplitude at the start of the selection down to silence at the end of the selection. The shape of the fade is linear. The rapidity of the fade-out depends entirely on the length of the selection it is applied to.

### Invert

Flips the audio samples upside-down. This normally does not affect the sound of the audio at all. It is occasionally useful for vocal removal.

### Leveller...

Leveller is a simple, combined compressor and limiter effect for reducing the dynamic range of audio. It reduces the difference between loud and soft, making the audio easier to hear in noisy environments or on small loudspeakers. It is best suited to speech recordings but at heavier settings or used multiple times it can also be used as a simple distortion effect for voices or instruments.

### Noise Removal...

Removes constant background noise such as fans, tape noise, or hums. It will not work very well for removing talking or music in the background. More details here.

### Normalize...

Use the Normalize effect to set the maximum amplitude of a track, equalize the amplitudes of the left and right channels of a stereo track and optionally remove any DC Offset from the track.

### Nyquist Prompt...

Launches a dialog where you can enter Nyquist commands. Nyquist is a programming language for producing and processing audio. For more information see Nyquist Plug-ins Reference.

### Paulstretch...

Use Paulstretch only for an extreme time-stretch or "stasis" effect. This may be useful for synthesizer pad sounds, identifying performance glitches or just creating interesting aural textures. Use Change Tempo or Sliding Time Scale rather than Paulstretch for tasks like slowing down a song to a "practice" tempo.

### Phaser...

The name "Phaser" comes from "Phase Shifter", because it works by combining phase-shifted signals with the original signal. The movement of the phase-shifted signals is controlled using a Low Frequency Oscillator (LFO).

### Repair

Fix one particular short click, pop or other glitch no more than 128 samples long.

### Repeat...

Repeats the selection the specified number of times.

### Reverse

Reverses the selected audio, so that it will sound as if it is playing from the end to the start.

### Sliding Time Scale / Pitch Shift...

Allows you to make a continuous change to the tempo and/or pitch of a selection by choosing initial and/or final change values.

Time Tracks can be used to bend tempo more flexibly (also affecting pitch) using Envelope Tool.

### Truncate Silence...

Automatically try to find and eliminate audible silences. Don't use with faded audio.

### Wahwah...

Rapid tone quality variations, like that guitar sound so popular in the 1970's.

Wahwah uses a moving bandpass filter to create its sound. A low frequency oscillator (LFO) is used to control the movement of the filter throughout the frequency spectrum.

The phase of the left and right channels is automatically adjusted when given a stereo track, so that the effect seems to travel across the speakers.

The following four classes of effect always appear underneath the divider in the Effect menu. Released builds of Audacity include sample Nyquist and/or LADSPA effects.

## Nyquist Effects

Nyquist plug-ins provide most of the optional effects underneath the divider in the Effect menu. They are also used to provide some of Audacity's built-in audio generators and analysis tools. A wide range of additional Nyquist effect, generation and analysis plug-ins can be obtained from Download Nyquist Plug-ins on our Wiki.

- To add a Nyquist plug-in, put it in the Audacity "Plug-ins" folder.
  - On Windows and OS X the "Plug-ins" folder is in the directory where Audacity resides - usually C:\Program Files on Windows or the "Applications" folder on OS X.
  - On Linux, the "plug-ins" folder is in usr/share/audacity if you installed an Audacity package supplied by your distribution, or usr/local/share/audacity if you compiled Audacity from source code. Optionally a plug-in folder can be created in the home directory ~/.audacity-files/plug-ins.
- The next time you launch Audacity, plug-ins you added will appear in the Effect, Generate or Analyze menus as appropriate.

The following sample Nyquist plug-ins are included in released builds of Audacity:

### Adjustable Fade...

Launches a dialog box where you can choose the shape of the fade in or fade out to be applied. You can also create fades to and from other than silence or full volume. An example of this might be a fade in from 20% of the original volume to 80% of the original volume.

### Clip Fix...

Attempts to reconstruct clipped regions by interpolating the lost signal.

### Cross Fade In

Applies a curve that will result in equal volume throughout the fade once the faded in and faded out regions are mixed.

### Cross Fade Out

Applies a curve that will result in equal volume throughout the fade once the faded in and faded out regions are mixed.

### Delay...

A configurable delay effect with variable delay time and pitch shifting of the delays.

### High Pass Filter...

Passes frequencies above its cut-off frequency and attenuates frequencies below its cut-off frequency; this can be used to reduce low frequency noise.

### Low Pass Filter...

Passes frequencies below its cut-off frequency and attenuates frequencies above its cut-off frequency; this can be used to reduce high pitched noise.

### Notch Filter...

Greatly attenuate ("notch out") a narrow frequency band. This is a good way to remove mains hum or a whistle confined to a specific frequency with minimal damage to the remainder of the audio.

### Studio Fade Out

Produces a smooth and musical sounding fade out, by applying a sinusoidal fade with a progressive low pass filter from full spectrum at the start of the selection to 100 Hz at the end.

### Tremolo...

Modulates the volume of the selection at the depth and rate selected in the dialog. The same as the tremolo effect familiar to guitar and keyboard players.

### Vocal Remover (for center-panned vocals)...

Attempts to remove center-panned audio from a stereo track; vocals are often (but not always) recorded in this way. Vocals (or other audio) can only be removed with this plug-in when panned to center, in other words sounding equally loud in both left and right channels. Help text is available from within the effect's dialog box.

### Vocoder...

Vocoder synthesizes a modulator (usually a voice) in the left channel of a stereo track with a carrier wave in the right channel to produce a modified version of the left channel. Vocoding a normal voice with white noise as provided in the effect will produce a robot-like voice for special effects. Other carriers can be used for subtly different voices. Vocoder can only be applied to unsplit stereo tracks.

## LADSPA Effects

LADSPA (Linux Audio Developer's Simple Plugin API) plug-ins were originally developed for the Linux platform, but ports of some plug-ins are available for Windows and OS X as well. Most LADSPA plug-ins are effects, but they are also used to provide some of Audacity's built-in audio generators and can be used for audio analysis. Additional LADSPA plug-ins can be downloaded for Windows, OS X and Linux.

- To add a LADSPA plug-in, put it in the Audacity "Plug-ins" folder.
  - On Windows and OS X the "Plug-ins" folder is in the directory where Audacity resides - usually C:\Program Files on Windows or the "Applications" folder on OS X.
  - On Linux, the "plug-ins" folder is in usr/share/audacity if you installed an Audacity package supplied by your distribution, or usr/local/share/audacity if you compiled Audacity from source code.
- The next time you launch Audacity, plug-ins you added will appear in the Effect, Generate or Analyze menus as appropriate.

Three sample LADSPA effects are included with Windows and Mac builds of Audacity:

### Hard Limiter...

An extreme compressor effect. It can sometimes be used to remove stubborn clicks.

### GVerb...

A reverb plug-in that adds ambience or "hall effect". Tips and example settings are available on our Wiki.

### SC4...

A stereo compressor with a variable envelope follower for RMS / peak behaviour.

Audacity will also load LADSPA plug-ins from the following system locations:

- All operating systems: The path specified by the LADSPA_PATH environment variable
- additionally on OS X:
  - ~/Library/Audio/Plug-Ins/LADSPA
  - /Library/Audio/Plug-Ins/LADSPA
- additionally on Linux/Unix:
  - $INSTALL_PREFIX/ladspa
  - /usr/local/lib/ladspa
  - $LIBDIR/ladspa

| Effects in the following VST and Audio Units (Mac only) classes are always third-party plug-ins added by the user (and also by the operating system in case of Audio Units)

## VST Effects

To add a VST effect on Windows or Mac, put its binary file (for example, the .dll file on Windows) in the Audacity "Plug-ins" folder. The "Plug-ins" folder should be in the same directory where Audacity resides.

1. Launch Audacity and go to the Effects tab of Preferences
2. Check Rescan VST effects next time Audacity is started and click OK
3. Quit and re-launch Audacity - the plug-ins you added will appear in the Effect menu

Note that the Rescan VST effects next time Audacity is started preference will now be un-checked. Audacity caches information about available VST effects rather than slow down each launch by scanning for VST effects. Therefore each time you add a new VST plug-in, it will be necessary to enable a launch-time rescan in Preferences.

When scanning, Audacity also looks for VST plug-ins in the following system locations:

- Windows and OS X: The path specified by the VST_PATH environment variable
- additionally on Windows:
  - Windows Registry key HKCU\Software\VST\VSTPluginsPath
  - Windows Registry key HKLM\Software\VST\VSTPluginsPath
- additionally on OS X:
  - ~/Library/Audio/Plug-Ins/VST
  - /Library/Audio/Plug-Ins/VST

## Audio Unit Effects

Audio Units (AU) are a system-level plug-in architecture provided on Mac OS X computers. To add an Audio Unit effect, place it in either of the following system plug-in directories:

- ~/Library/Audio/Plug-Ins/Components (user plug-ins)
- /Library/Audio/Plug-Ins/Components (system-wide plug-ins)

The next time you launch Audacity, newly added plug-ins will appear underneath the divider in the Effect menu.

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