Glossary of terms and abbreviations

When an instrument is able to play more than one note at a time, it is said to be polyphonic. Pianos, organs, and guitars are all polyphonic instruments. Most electronic instruments have a limit to the number of notes they can play simultaneously, and this is referred to as the polyphony of the device. For example, a device which can sound up to 30 independent note is said to be 30 note polyphonic.
Refers to an instrument which is only capable of playing one note at a time. For example, the flute and the trumpet are monophonic instruments.
Portamento is where a note is allowed to 'slide' up or down in frequency from a previous note, rather than making an abrupt change. This effect is difficult to apply effectively on a polyphonic device, but lends itself well to monophonic devices.
Omni mode
A MIDI receiver normally only responds to Channel Voice messages on one particular MIDI Channel. If the receiver mode is changed to 'Omni On', the receiver will respond to Channel Voice messages on any MIDI channel.
A single note which may be sounded by a MIDI device. The number of simultaneous voices which a device may sound is also referred to as the 'polyphony' of the device.

Although technically a single 'note' may use more than one voice in a MIDI device (depending on the configuration of the device), throughout this document it is assumed that a note will only use a single voice, and hence the terms 'note' and 'voice' are used interchangeably.

The amplitude of a sound as it changes over time.
The 'envelope' of a note played on a synthesizer is often divided into a number of time-regions:
  • Attack
  • Decay
  • Sustain
  • Release
Short for System Exclusive, see MIDI System Exclusive Messages
MIDI Time Code