The MIDI specification provides for 16 different channels. Each channel may be used to control an independent voice. The voices may be played on one or several synthesizers. Performance events generally result in Channel Voice messages. Performance events include, key events, foot switch events, and continuous controller events (mod wheels, breath controllers, guitar string bends, turning on lights, etc.).
Channels are numbered from 1-16. Once a voice is assigned to a channel number, Channel Voice messages with other channel numbers are ignored. In networking, this is said to be a form of Medium Access Control (MAC). For the purpose of transmission efficiency, all of the messages are put into a packed binary format.
There are 7 different MIDI Channel Voice messages, Note On, Note Off, Pitch Bender Change, Control Change, Polyphonic Key Pressure, Channel Pressure and Program Change. They are characterized by a status word followed by one or two data words. Each word is 8 bits in length. MIDI Channel Voice message data words range from 0-127. The least significant 4 bits of each MIDI status word contains the channel number. The following 7 subsections detail the MIDI Channel Voice messages.
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