Recording · glossary
AUv3
Also called Audio Unit, AU plugin, iOS plugin
AUv3 (Audio Unit version 3) is Apple's plugin format for iPhone, iPad and Mac. An AUv3 instrument or effect comes inside a regular App Store app and can also load inside a host app, such as GarageBand, as the sound or effect on one track.
Apple introduced version 3 of its Audio Unit format in 2015, with iOS 9 and OS X El Capitan, and built it on app extensions. That is why an AUv3 needs no separate installer. You download the app from the App Store, and its plugin shows up in any host app that supports AUv3. In GarageBand on iPhone, open the Sound browser, swipe to External and tap Audio Unit Extensions to find them.
These are the kinds you will meet most:
- Instruments: synths, drum machines and samplers, played from a MIDI track or the host’s own keyboard.
- Effects: reverbs, delays, compressors and amp simulators that process a track’s audio.
- MIDI effects (MIDI processors, in Apple’s terms): arpeggiators, chord tools and sequencers that change or create notes before they reach an instrument.
Running a synth as a plugin changes how you work. Played on its own and recorded, a synth app gives you audio, and the sound is fixed once it is recorded. Loaded as an AUv3 in a DAW, the same synth plays from editable MIDI notes and its settings are saved with the song. You can often load it on several tracks at once with a different sound on each, and when you reopen the project next week every track sounds the way you left it.
On a Mac, many plugins still come as the older Audio Unit version (AUv2) or as VSTs. On iPhone and iPad, AUv3 is the plugin format, and hosts include GarageBand, Cubasis, AUM and Loopy Pro, plus Logic Pro on iPad. App listings usually say “AUv3” or “Audio Unit” in the description when an app supports it.
Our list of the best synth apps for iPhone notes which ones run as AUv3 inside GarageBand, and GarageBand alternatives for iPhone covers hosts that go further.
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