# 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.

## 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...

This effect 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.

### BassBoost...

This is a smooth filter which can amplify the lower frequencies while leaving most of the other frequencies alone. It behaves just like the bass control on a stereo. As with Equalization, amplifying particular frequencies can result in clipping, so it is recommended to Effect > Normalize the track(s) first to -3 dB or lower. If necessary you can always Edit > Undo the Bass Boost, Normalize again to a lower level, then re-apply Bass Boost.

### 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 linear fade-in to the selected audio - the rapidity of the fade-in depends entirely on the length of the selection it is applied to.

### Fade Out

Applies a linear fade-out to the selected audio - the rapidity of the fade-out depends entirely on the length of the selection it is applied to.

By repeating a fade in, the audio will remain quiet for longer then rise more rapidly to the original level. Similarly, repeating a fade out will cause the level to initially drop more rapidly then tail off at a lower level. As with other effects, the fade may be repeated as required by pressing CTRL + R.

For a more customizable logarithmic fade in or fade out, use the Envelope Tool on the Tools Toolbar.

### Invert

This effect flips the audio samples upside-down. This normally does not affect the sound of the audio at all. It is occasionally useful, for example when the left and right channels of a song both contain equal amounts of vocals, but unequal amounts of background instruments. By inverting one of the channels and not the other and then converting from stereo to mono, the vocals will cancel each other out, leaving just the instrumentals. This only works if the exact same vocal signal is present in both of the channels to begin with.

### Leveller...

The Leveller effect makes quiet passages louder and loud passages quieter. It does this in a way that is different from the Compressor effect. As a result it does add some distortion to the processed audio. The only way to be sure if the effect does what you want is to try it. For example, applying this effect twice at its Heaviest setting on a normally-recorded voice can produce an "air traffic controller" effect.

### Noise Removal...

This effect is ideal for removing 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...

This brings up 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

This effect reverses the selected audio temporally; after the effect the end of the audio will be heard first and the beginning last. Some people reverse small portions of audio to make inappropriate language unintelligible, while others believe you can hear subliminal messages if you listen to speech backwards. You can also create interesting sound effects by recording natural events and reversing the audio.

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

This effect 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.

This effect 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 WahWah effect automatically adjusts the phase of the left and right channels when given a stereo recording, 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:

### Clip Fix...

This effect attempts to reconstruct clipped regions by interpolating the lost signal.

### Cross Fade In

Despite the name this effect does not do an automatic cross fade between two tracks or clips. Instead it applies a curve that is different from the one used by the Fade In effect. The curve used is one that will result in equal volume throughout the fade once the faded in and faded out regions are mixed.

### Cross Fade Out

Despite the name this effect does not do an automatic cross fade between two tracks or clips. Instead it applies a curve that is different from the one used by the Fade Out effect. The curve used is one 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 cutoff frequency and attenuates frequencies below its cutoff frequency; this can be used to reduce low frequency noise.

### Low Pass Filter...

Passes frequencies below its cutoff frequency and attenuates frequencies above its cutoff 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.

### 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.

"dB limit" is the input signal level above which the input signal will be clipped.

"Wet level" controls the amount of the clipped signal fed to the output. It thus acts as a volume control applied after the limiter (just as if you applied the effect and then used the Amplify effect).

"Residue level" controls the amount of the clipped signal that will be mixed back in. By default the value is set to zero and so the clipped signal is discarded. By raising this level, some of the clipped signal will be restored, making the limit softer and retaining more of the peaks and troughs of the original waveform. Alternatively if you turn the residue full up and the Wet signal full down, you get only the pieces of waveform that are above the dB limit you chose.

### GVerb...

A reverb plug-in. 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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