# General Audio Unit Function Selectors General audio unit component selectors that correspond to functions in the audio unit API. ## Topics ### Constants [`var kAudioUnitAddPropertyListenerSelect: Int`](/documentation/AudioToolbox/kAudioUnitAddPropertyListenerSelect) Used by the system to register a property listener callback function for an audio unit when you call the [`AudioUnitAddPropertyListener(_:_:_:_:)`](/documentation/AudioToolbox/AudioUnitAddPropertyListener(_:_:_:_:)) function. [`var kAudioUnitAddRenderNotifySelect: Int`](/documentation/AudioToolbox/kAudioUnitAddRenderNotifySelect) [`var kAudioUnitComplexRenderSelect: Int`](/documentation/AudioToolbox/kAudioUnitComplexRenderSelect) [`var kAudioUnitGetParameterSelect: Int`](/documentation/AudioToolbox/kAudioUnitGetParameterSelect) Used by the system to get the current value of an audio unit parameter when you call the [`AudioUnitGetParameter(_:_:_:_:_:)`](/documentation/AudioToolbox/AudioUnitGetParameter(_:_:_:_:_:)) function. [`var kAudioUnitGetPropertyInfoSelect: Int`](/documentation/AudioToolbox/kAudioUnitGetPropertyInfoSelect) Used by the system to get property information from an audio unit when you call the [`AudioUnitGetPropertyInfo(_:_:_:_:_:_:)`](/documentation/AudioToolbox/AudioUnitGetPropertyInfo(_:_:_:_:_:_:)) function. [`var kAudioUnitGetPropertySelect: Int`](/documentation/AudioToolbox/kAudioUnitGetPropertySelect) [`var kAudioUnitInitializeSelect: Int`](/documentation/AudioToolbox/kAudioUnitInitializeSelect) [`var kAudioUnitProcessMultipleSelect: Int`](/documentation/AudioToolbox/kAudioUnitProcessMultipleSelect) [`var kAudioUnitProcessSelect: Int`](/documentation/AudioToolbox/kAudioUnitProcessSelect) [`var kAudioUnitRange: Int`](/documentation/AudioToolbox/kAudioUnitRange) [`var kAudioUnitRemovePropertyListenerSelect: Int`](/documentation/AudioToolbox/kAudioUnitRemovePropertyListenerSelect) Used by the system to unregister a property listener callback function from an audio unit when you call the `AudioUnitRemovePropertyListener` function. [`var kAudioUnitRemovePropertyListenerWithUserDataSelect: Int`](/documentation/AudioToolbox/kAudioUnitRemovePropertyListenerWithUserDataSelect) [`var kAudioUnitRemoveRenderNotifySelect: Int`](/documentation/AudioToolbox/kAudioUnitRemoveRenderNotifySelect) [`var kAudioUnitRenderSelect: Int`](/documentation/AudioToolbox/kAudioUnitRenderSelect) Used by the system to invoke audio rendering by an audio unit when you call the [`AudioUnitRender(_:_:_:_:_:_:)`](/documentation/AudioToolbox/AudioUnitRender(_:_:_:_:_:_:)) function. [`var kAudioUnitResetSelect: Int`](/documentation/AudioToolbox/kAudioUnitResetSelect) Used by the system to reset an audio unit when you call the [`AudioUnitReset(_:_:_:)`](/documentation/AudioToolbox/AudioUnitReset(_:_:_:)) function. [`var kAudioUnitScheduleParametersSelect: Int`](/documentation/AudioToolbox/kAudioUnitScheduleParametersSelect) Used by the system to schedule an audio unit parameter value change when you call the [`AudioUnitScheduleParameters(_:_:_:)`](/documentation/AudioToolbox/AudioUnitScheduleParameters(_:_:_:)) function. [`var kAudioUnitSetParameterSelect: Int`](/documentation/AudioToolbox/kAudioUnitSetParameterSelect) Used by the system to set the value of an audio unit parameter when you call the [`AudioUnitSetParameter(_:_:_:_:_:_:)`](/documentation/AudioToolbox/AudioUnitSetParameter(_:_:_:_:_:_:)) function. [`var kAudioUnitSetPropertySelect: Int`](/documentation/AudioToolbox/kAudioUnitSetPropertySelect) [`var kAudioUnitUninitializeSelect: Int`](/documentation/AudioToolbox/kAudioUnitUninitializeSelect) Used by the system to uninitialize an audio unit when you call the [`AudioUnitUninitialize(_:)`](/documentation/AudioToolbox/AudioUnitUninitialize(_:)) function. --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)