Audio messages are sent by low-level audio device drivers to an application so that the application can manage audio playback and recording. An application may choose to have audio messages sent either to a window, or to a low-level callback function. There is a set of messages for windows and a parallel set of messages for low-level callback functions. The Multimedia extensions provide the following groups of audio messages:
Waveform Output Messages
Waveform Input Messages
MIDI Output Messages
MIDI Input Messages