Audio Units (AU) are a system-level plug-in architecture provided by Core Audio in

Apple An apple is a round, edible fruit produced by an apple tree (''Malus'' spp.). Fruit trees of the orchard or domestic apple (''Malus domestica''), the most widely grown in the genus, are agriculture, cultivated worldwide. The tree originated ...

macOS macOS, previously OS X and originally Mac OS X, is a Unix, Unix-based operating system developed and marketed by Apple Inc., Apple since 2001. It is the current operating system for Apple's Mac (computer), Mac computers. With ...

and iOS operating systems. Audio Units are a set of

application programming interface An application programming interface (API) is a connection between computers or between computer programs. It is a type of software Interface (computing), interface, offering a service to other pieces of software. A document or standard that des ...

(API) services provided by the

operating system An operating system (OS) is system software that manages computer hardware and software resources, and provides common daemon (computing), services for computer programs. Time-sharing operating systems scheduler (computing), schedule tasks for ...

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 another popular plug-in format, Steinberg's Virtual Studio Technology (VST). Because of the many similarities between Audio Units and VST, several commercial and free wrapping technologies are available (e.g
Symbiosis
and FXpansionbr>VST-AU Adapter
. Celemony Software and PreSonus have also developed the Audio Random Access (ARA) extension, which works for both AU and VST, allowing greater integration between the plug-ins and DAW software.

Use

Audio Units allows sound file audio time stretching and pitch scaling (e.g., timestretch),

sample rate In signal processing, sampling is the reduction of a continuous-time signal to a discrete-time signal. A common example is the conversion of a sound wave to a sequence of "samples". A sample is a value of the signal at a point in time and/or ...

conversion, and streaming over a

local area network A local area network (LAN) is a computer network that interconnects computers within a limited area such as a residence, campus, or building, and has its network equipment and interconnects locally managed. LANs facilitate the distribution of da ...

. It also comes with a set of AU plug-ins such as EQ filters, dynamic processors, delay, reverb, and a Soundbank Synthesizer Instrument. AU are used by Apple applications such as

GarageBand GarageBand is a software application by Apple Inc., Apple for macOS, iPadOS, and iOS devices that allows users to create music or Podcast, podcasts. It is a lighter, amateur-oriented offshoot of Logic Pro. GarageBand was originally released for ...

, Soundtrack Pro, Logic Express, Logic Pro, Logic Pro X, Final Cut Pro, MainStage and most 3rd party audio software developed for

such as Ableton Live, Amadeus Pro, Ardour, Audio Hijack,

DaVinci Resolve DaVinci Resolve is a proprietary color grading, color correction, visual effects, and audio post-production video editing application for macOS, Windows, and Linux, developed by Australian company Blackmagic Design. It was originally deve ...

, Digital Performer, Gig Performer, REAPER, and Studio One.

Competing technologies

* Avid's Avid Audio eXtension (a successor to the RTAS format) * Digidesign's Real Time AudioSuite (now obsolete) * LADSPA and Disposable Soft Synth Interface (DSSI) for

Linux Linux ( ) is a family of open source Unix-like operating systems based on the Linux kernel, an kernel (operating system), operating system kernel first released on September 17, 1991, by Linus Torvalds. Linux is typically package manager, pac ...

* LV2 (crossplatform successor to LADSPA) *

Microsoft Microsoft Corporation is an American multinational corporation and technology company, technology conglomerate headquartered in Redmond, Washington. Founded in 1975, the company became influential in the History of personal computers#The ear ...

DirectX Microsoft DirectX is a collection of application programming interfaces (APIs) for handling tasks related to multimedia, especially game programming and video, on Microsoft platforms. Originally, the names of these APIs all began with "Direct" ...

* Steinberg's Virtual Studio Technology

References

{{OS X Music software plugin architectures macOS APIs