audio units (AU) are a system-level plug-in architecture provided by Core Audio in Mac OS X developed by Apple Computer. audio units are a set of application programming interface services provided by the operating system to generate, process, receive, or otherwise manipulate streams of audio in near-real-time with minimal latency. It may be thought of as Apple's architectural equivalent to the other popular plug-in format, Steinberg's VST.
Usage
Mac OS X comes with audio units allowing to timestretch an audio file, convert its sample rate and stream audio over a Local Area Network. It also comes with a collection of AU plug-ins such as EQ filters, dynamic processors, delay, reverb, and a Soundbank Synthesizer Instrument.