On a synth which is under MIDI control, a note that does not stop sounding when it is supposed to, because the MIDI receiver failed to receive a note off message for that note. This may occur because of a sequencer software error (the software "loses track" of which notes are being played), or because the note off message was lost or corrupted in transmission. Without receiving the note off message, the synth will continue to sound the note indefinitely. The purpose of the MIDI all notes off message is to get rid of stuck notes. See also panic button.