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# Mixer Audio Unit Subtypes

Audio mixing audio unit subtypes for audio units provided by Apple.

## Topics

### Constants

[`var kAudioUnitSubType_MatrixMixer: UInt32`](/documentation/AudioToolbox/kAudioUnitSubType_MatrixMixer)

[`var kAudioUnitSubType_MultiChannelMixer: UInt32`](/documentation/AudioToolbox/kAudioUnitSubType_MultiChannelMixer)

An audio unit that can have any number of input buses, with any number of channels on each input bus, and one output bus. In macOS, the output bus can have any number of channels. In iOS, the output bus always has two channels.

[`var kAudioUnitSubType_SpatialMixer: UInt32`](/documentation/AudioToolbox/kAudioUnitSubType_SpatialMixer)


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