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

Apple An apple is an edible fruit produced by an apple tree (''Malus domestica''). Apple fruit tree, trees are agriculture, cultivated worldwide and are the most widely grown species in the genus ''Malus''. The tree originated in Central Asia, wh ...

macOS macOS (; previously OS X and originally Mac OS X) is a Unix operating system developed and marketed by Apple Inc. since 2001. It is the primary operating system for Apple's Mac computers. Within the market of desktop and lapt ...

and

iOS iOS (formerly iPhone OS) is a mobile operating system created and developed by Apple Inc. exclusively for its hardware. It is the operating system that powers many of the company's mobile devices, including the iPhone; the term also includes ...

operating systems. Audio Units are a set of

application programming interface An application programming interface (API) is a way for two or more computer programs to communicate with each other. It is a type of software interface, offering a service to other pieces of software. A document or standard that describes how t ...

(API) services provided by the

operating system An operating system (OS) is system software that manages computer hardware, software resources, and provides common services for computer programs. Time-sharing operating systems schedule tasks for efficient use of the system and may also in ...

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 Virtual Studio Technology (VST) is an audio plug-in software interface that integrates software synthesizers and effects units into digital audio workstations. VST and similar technologies use digital signal processing to simulate traditional rec ...

(VST). Because of the many similarities between Audio Units and VST, several commercial and free wrapping technologies are available (e.g
Symbiosis
and

FXpansion FXpansion is a Ltd company that produces music software including Geist2, Strobe2, Tremor, Etch, Bloom, Maul and DCAM Dynamics. History FXpansion is a company that develops music software, and was founded in 1999 in London, United Kingd ...

br>VST-AU Adapter
. Celemony Software and

PreSonus PreSonus Audio Electronics, Inc. (often known and styled as PreSonus) is an American manufacturer of professional audio equipment and software, used to create, record, Audio mixing, mix, and Audio mastering, master music and other audio. This inc ...

have also developed the Audio Random Access (ARA) extension, which works for both AU and

VST VST may refer to: * Vancouver School of Theology, a theological graduate school in British Columbia, Canada * VST, Stockholm Västerås Airport in Sweden (IATA airport code) * Vehicle safety technology * Virtual Studio Technology, Steinberg's stand ...

, allowing greater integration between the plug-ins and

DAW Daw or DAW may refer to: People and language * Daw (given name) * Daw (surname) * Daw, an honorific used in Burmese name#Honorifics, Burmese names * Dâw people, an indigenous people of Brazil * Dâw language, a language of Brazil * Davaoeño lang ...

software.

Use

Audio Units allows sound file audio time stretching and pitch scaling (e.g., timestretch), sample rate 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, school, laboratory, university campus or office building. By contrast, a wide area network (WAN) not only covers a larger ...

. 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 line of digital audio workstations developed by Apple Inc. for macOS, iPadOS, and iOS devices that allows users to create music or podcasts. GarageBand is developed by Apple for macOS, and was once part of the iLife software s ...

, Soundtrack Pro,

Logic Express Logic Express was a "light" version of Logic Pro, a MIDI sequencer and digital audio workstation software application maintained by Apple that runs on the Mac OS X platform. It was announced on January 15, 2004, for release in March 2004. Logic ...

, Logic Pro,

Logic Pro X Logic Pro is a digital audio workstation (DAW) and MIDI sequencer software application for the macOS platform. It was originally created in the early 1990s as Notator Logic, or Logic, by German software developer C-Lab which later went by E ...

, Final Cut Pro,

MainStage MainStage is a music application developed by Apple Inc. designed for use in live performance. Features MainStage might be thought of as a companion app to Logic Pro. It works in much the same way and bears a similar user interface. The focu ...

and most 3rd party audio software developed for

such as Ableton Live, Amadeus Pro, Ardour,

Audio Hijack Rogue Amoeba Software, Inc. is a software company that produces audio software, specializing in applications for audio capture for the Macintosh platform. Rogue Amoeba's best-known products are Audio Hijack and Audio Hijack Pro (both now known si ...

, DaVinci Resolve,

Digital Performer Digital Performer is a digital audio workstation and music sequencer software package published by Mark of the Unicorn (MOTU) of Cambridge, Massachusetts for the Apple Macintosh and Microsoft Windows platforms. Ancestry In 1984, Mark of the Un ...

Gig Performer Gig Performer is a cross-platform audio plug-in host software package developed by Deskew Technologies. It is designed to provide a solution for playing an instrument and effect plug-ins live, without using a DAW. It was originally released in ...

, REAPER, and

Studio One Studio One or Studio 1 may refer to: * Studio One (software), digital audio workstation software, developed by PreSonus * ''Studio One'' (American TV series), a 1948–1958 American television anthology series * ''Studio One'' (Emirati TV progra ...

Competing technologies

* Avid's Avid Audio eXtension (a successor to the RTAS format) * Digidesign's

Real Time AudioSuite Real-Time AudioSuite (RTAS) is a format of audio plug-in developed by Digidesign, currently Avid Technology for their Pro Tools LE and Pro Tools M-Powered systems, although they can be run on Pro Tools HD and Pro Tools TDM systems. RTAS plug-i ...

(now obsolete) *

LADSPA LADSPA is an acronym for Linux Audio Developer's Simple Plugin API. It is an application programming interface (API) standard for handling audio filters and audio signal processing effects, licensed under LGPL-2.1-or-later. It was originally de ...

and

Disposable Soft Synth Interface Disposable Soft Synth Interface (DSSI) is a virtual instrument ( software synthesizer) plugin architecture for use by music sequencer applications. It was designed for applications running under Linux, although there is nothing specific to Linu ...

(DSSI) for

Linux Linux ( or ) is a family of open-source Unix-like operating systems based on the Linux kernel, an operating system kernel first released on September 17, 1991, by Linus Torvalds. Linux is typically packaged as a Linux distribution, which ...

LV2 LV2 (LADSPA Version 2) is a set of royalty-free open standards for plug-ins and matching host applications. It includes support for the synthesis and processing of digital audio and CV, events such as MIDI and OSC, and provides a free alte ...

(crossplatform successor to LADSPA) *

Microsoft Microsoft Corporation is an American multinational technology corporation producing computer software, consumer electronics, personal computers, and related services headquartered at the Microsoft Redmond campus located in Redmond, Washing ...

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

References

Music software plugin architectures macOS APIs {{mac-stub