An interface to a set of audio tone player callback functions.

The class is a mixin and is intended to be inherited by the client class which is observing the audio tone playing operation. The functions encapsulated by this class are called when specific events occur in the process of preparing to play a tone and during the playing of a tone. A reference to this object is passed as a parameter when constructing an audio tone player utility, using the CMdaAudioToneUtility interface.