Audio Units

This page describes support for Audio Unit effect plug-ins in Audacity. Audio Units is a plug-in architecture developed by Apple and is only supported in Audacity 1.3.1 and later on Mac OS X.

Related article(s): Ladspa Plug-ins Nyquist Plug-ins VST Plug-ins Other pages in our Plug-ins category Building Audio Units plug-ins using Xcode

Audio Unit support

Audio Unit (AU) support is available in Audacity 1.3.1 and later - Audacity scans for available AU plug-ins each time it launches. AU support is enabled by default, but it can be turned on or off by clicking Audacity > Preferences: Effects then under "Enable Effects", uncheck "Audio Unit". Restart Audacity for changes to take effect.

Audio Unit "MusicEffects" are supported in Audacity 1.3.14 and later. This class of Audio Unit supports audio input like pure "Effect" AU's but has the ability to use MIDI input to set effect parameters. Audacity doesn't yet accept MIDI input, so although MusicEffects should work fine as audio effects, parameters need to be set manually. Examples of MusicEffects are all those from DestroyFX, Ohm Force and SFXmachine, plus FXpansion Snippet, Tobybear MadShifta and u-he MFM2.

Like VST plug-ins in current Audacity, Audio Units display their full GUI interface by default, where one is provided. If interface difficulties arise, Audio Units can be limited to a tabular interface with sliders by unchecking the option "Display Audio Unit effects in graphical mode" at Audacity > Preferences: Effects. Once again, restart Audacity for changes to take effect.

There are some screenshots of Audio Units plug-ins in Audacity here.. You can find a useful list of third-party AU plug-ins (free and demo/paid-for) on Hitsquad.

To add new Audio Units (AU) plug-ins, place them in:

• /Library/Audio/Plug-Ins/Components/ or
• ~/Library/Audio/Plug-Ins/Components/

and restart Audacity. As always, ~ means your home directory. Audacity will not load Audio Unit plug-ins from the Audacity "Plug-ins" folder.

Issues

Antares Auto-Tune Evo

This plug-in only has a tabular interface which is apparently a problem in some other Audio Unit hosts also.

Apple AU GraphicEQ

AU GraphicEQ has an inherent limitation that it cannot be resized in use, so that if more bands are selected than fit on the screen, not all the selected bands will be accessible. As a workaround, close the plug-in with the required number of bands selected, then re-open it. All the selected bands will now be accessible.

Apple AU MatrixReverb

AU MatrixReverb only outputs in stereo and needs a stereo track to work on, so cannot be used on a mono track. It seems to be the only one of the built-in Audio Units plug-ins that has this limitation. For a workaround, select the track by clicking in its Track Control Panel above the Mute/Solo buttons, then Edit > Duplicate. Click on the drop-down arrow in the Track Control Panel of the upper track > Make Stereo Track. After processing with AU MatrixReverb, click the arrow again > Split Stereo Track, click the arrow once more in the upper track and make it Mono, then delete the lower track by clicking on the [X] in the Track Control Panel.

Slow launch or hang

Some older third-party AU plug-ins can be very slow to load (and to unload on exit); launch can take several minutes if you have a large number of AU plug-ins. There is no real solution at present other than removing troublesome plug-ins from the "Components" folder as above, or disable all AU effects in Audacity in the Effects Preferences. If you identify any single AU plug-ins that are problematic in Audacity, please contact our feedback address.

If Audacity does not launch at all, you can disable AU support in Audacity using the audacity.cfg settings file. Force quit Audacity (Option - Command - Esc). In Finder, use Go > Go to Folder then type in ~/Library/Application Support/audacity/. Look in that "audacity" folder for audacity.cfg.

Open audacity.cfg in TextEdit. If Audacity has never quit cleanly, you may need to create audacity.cfg by using File > New in TextEdit.

To disable Audio Units you want to edit (or add) an "AudioUnits" entry to audacity.cfg so it looks like this:

[AudioUnits]
Enable=0
GUI=0

If you are creating audacity.cfg from scratch, enter all these lines:

NewPrefsInitialized=1
[AudioUnits]
Enable=0
GUI=0

Then save the changes to audacity.cfg and restart Audacity. If Audacity still hangs then the problem could be with VST Plug-ins. If you don't need VST plug-ins in Audacity, you can edit/create audacity.cfg so that VST plug-ins are also disabled:

NewPrefsInitialized=1
[AudioUnits]
Enable=0
GUI=0
[VST]
Enable=0
GUI=0
Rescan=0