A MIDI message that tells an instrument to stop playing a note. It consists of a status byte that identifies itself and the MIDI channel affected, a data byte that identifies the MIDI note number, and a data byte that establishes the release velocity.
In earlier MIDI instruments Note Off was rarely employed due to the expense of building keyboards with sensors that could detect release velocity. Instead, these instruments would issue a Note On message with a velocity of “0” to signify the end of a note. However, with increasingly powerful processors, more complex voice programming, and especially with more elaborate sample libraries that include (for example) the triggering of “release” samples in string instruments, note off messages have taken on more significance.