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# Generator Audio Unit Subtypes

Audio units that serve as sound sources.

## Topics

### Constants

[`var kAudioUnitSubType_AudioFilePlayer: UInt32`](/documentation/AudioToolbox/kAudioUnitSubType_AudioFilePlayer-6zi0a)

[`var kAudioUnitSubType_ScheduledSoundPlayer: UInt32`](/documentation/AudioToolbox/kAudioUnitSubType_ScheduledSoundPlayer-55u1s)

A generator unit that can be used to schedule slices of audio to be played at specified times. The audio is scheduled using the time stamps for the render operation and can be scheduled from any thread.


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