The underlying Core Audio audio unit.
- iOS 8.0+
- macOS 10.10+
- UIKit for Mac 13.0+Beta
- tvOS 9.0+
A reference to the underlying audio unit is provided so that parameters that are not exposed by
AVAudio subclasses can be modified using the AudioUnit C API.
No operations that may conflict with state maintained by the engine should be performed directly on the audio unit. These include changing initialization state, stream formats, channel layouts or connections to other audio units.