## MMPM/2 Device Driver Reference

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### Types of MIDI Messages

There are three types of MIDI system messages:

System common
System exclusive
System real time

System-common messages are intended for all receivers, regardless of channel. System-exclusive messages are defined by the manufacturer and are not limited in length. System-real-time messages can interrupt other messages because they carry timing information. For example, a long system message might have an embedded timer message within it. Other MIDI events cannot occur within a system message or nested system message; however, a system message can occur in the middle of other MIDI events.

While in MIDI mode, almost all functions provided by audio device drivers can be controlled by the application by using system-exclusive messages.