What is MIDI Polyphonic Expression (MPE)?
MPE is a way of using MIDI that allows more detailed and expressive control over individual notes. It stands for MIDI Polyphonic Expression. With normal MIDI 1.0, all notes on a channel share the same controls, like pitch bend or modulation. This means you can’t easily bend just one note in a chord — you’d affect all the notes at once.
MPE changes that. It makes it possible to apply things like pitch bend, filter changes, or pressure to each note separately. This gives you more control and lets electronic instruments behave more like real acoustic instruments.
How MPE Works
MPE still uses MIDI 1.0, but in a clever way. Normally, you’d use one channel for one instrument or part. With MPE, each note you play is given its own MIDI channel. For example, if you play three notes, one might be sent on channel 2, the next on channel 3, and the third on channel 4.
Each of these channels has its own pitch bend, modulation, and other controls. That means you can slide, press, or bend one note without affecting the others. It feels more natural, especially when using instruments like the ROLI Seaboard or a MIDI guitar, where you move your fingers in different ways on each note.
MPE sets aside a block of channels (usually 2–16) for this purpose, while one channel (channel 1 by default) acts as the master channel for general settings like program changes or volume.
The Difference with Standard MIDI 1.0
In regular MIDI 1.0, all notes on the same channel share the same control values. This works fine for simple instruments, but it limits expression. For example, if you want to bend just one note in a chord, you can’t — pitch bend affects the whole channel. MPE solves this by giving each note its own channel, so you can shape each note differently. It uses MIDI 1.0 messages, just spread across multiple channels.
Difference with MIDI 2.0
MIDI 2.0 includes per-note expression directly in the protocol. You don’t need to split notes across channels anymore. In MIDI 2.0, all notes can be controlled individually on the same channel, with much higher resolution — up to 32-bit control instead of 7-bit or 14-bit.
While MPE is a smart workaround using MIDI 1.0, MIDI 2.0 is a cleaner and more powerful solution. It does everything MPE can, and more — with better timing, higher precision, and simpler setup. That said, MPE works today and is supported by many devices, while MIDI 2.0 is still being adopted.
Benefits for Musicians
MPE lets you play more expressively. You can bend one note in a chord, press harder on some notes for more volume or brightness, or slide between notes smoothly. This makes electronic instruments feel more lifelike and responsive. It’s especially useful for touch-sensitive controllers and MIDI guitars, where each finger moves differently.
Because MPE is based on MIDI 1.0, it works with many modern synths and DAWs. It gives you much more musical control without needing completely new gear. For now, it’s the best way to get per-note expression — until MIDI 2.0 becomes more common.