High Quality Content by WIKIPEDIA articles! 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. Because of the many similarities between Audio Units and VST several commercial and free wrapping technologies are available (e.g. Symbiosis and FXpansion VST-AU Adapter).