A dual-message MIDI event consisting of a note on message — a three-byte message consisting of a status byte identifying the event as a note and the MIDI channel number of the note, a byte containing the MIDI note number, and a byte containing a velocity value.
A note off message is required to complete the MIDI note — a MIDI note contains no duration information, so a note off is required to stop the note from sounding. The note off message includes a status byte identifying the event as a note and the MIDI channel number of the note, a byte containing the MIDI note number, and a byte containing a release velocity value.