MIDI Polyphonic Expression (MPE) is an “extension” to the MIDI 1.0 specification that is designed to allow independent control of each individual note in a polyphonic performance.
MPE works by assigning each new note played to a separate MIDI channel, such that modulations can be distinctly specified for each note.
MPE does not involve any changes to the MIDI 1.0 standard. Rather, MPE provides an approach to using MIDI 1.0 in a way to achieve independent note control, which is generally limited to 15 notes at a time because one channel is reserved for global messages.
