How does the MIDI system work?
Channel Voice Messages Almost all MIDI devices are equipped to receive MIDI messages on one or more of 16 selectable MIDI channel numbers. A device’s particular voice (or patch, program, timbre) will respond to messages sent on the channel it is tuned to and ignore all other channel messages, analogous to a television set receiving only the station it is tuned to and rejecting the others. The exception to this is OMNI mode. An instrument set to receive in OMNI mode will accept and respond to all channel messages, regardless of the channel number. The most common MIDI messages are channel voice messages listed in the chart below. They convey information about whether to turn a note on or off, what patch to change to, how much key pressure to exert (called aftertouch), etc.
