MPE guide

MPE (MIDI Polyphonic Expression) lets each note you play carry its own pitch, timbre, and pressure data. Instead of one channel for all notes, each note gets its own channel — so a finger slide on one pad bends only that note, not every note currently held.

Mobile MIDI's pads and keyboard support MPE out of the box.

When to use MPE

You want per-note pitch bend — slide a finger on a pad and only that pad's note bends.
You want per-note pressure — press harder on one pad and only that pad changes timbre.
Your synth supports MPE (most modern soft synths do — Arturia Pigments, Equator, Serum 2, Roli Equator, Ableton Wavetable/Instrument Rack in MPE mode, etc.).

If your synth doesn't support MPE, leave MPE off — the regular monophonic-per-channel output will be more compatible.

Turning MPE on

On the Touch tab, with Pads or Keys selected, toggle the MPE switch at the top of the screen (purple).

When MPE is on:

Each new note is allocated its own MIDI channel from channels 2 through 16 (channel 1 is the "master" channel for global messages).
Channels are reused in LRU (least-recently-used) order — up to 15 simultaneous notes.
Pressure slide, pitch bend, and aftertouch are sent per channel, so each note expresses independently.

Setting up your synth

Your synth needs to be in MPE mode to receive these messages correctly. In most DAWs:

Ableton Live 11+ — use the MPE-aware track setting on a Drum Rack or an MPE-compatible instrument.
Logic Pro — Project Settings → MIDI → Multi-player mode, and make sure your track accepts MPE.
Hardware synths — consult the manual; look for "MPE mode" in the global settings.

What gets sent in MPE mode

For each note you play on a pad or key:

Note On / Note Off — on the allocated channel.
Channel Pressure (or poly aftertouch, depending on synth setup) — from the pressure you apply while pressing.
Pitch Bend — from horizontal finger slide, on the note's channel.
CC 74 (timbre) — from vertical finger slide, on the note's channel (when enabled).

Pads vs keys in MPE

Pads — most useful for per-note pressure and a subtle pitch wobble.
Keys — more useful for pitch bends (slide along the key face) and vibrato.

Turning MPE off

Tap the MPE switch off. All notes now share channel 1 — classic MIDI. This is the right mode if your synth is not MPE-aware.

Common pitfalls

All notes bend together — your synth isn't in MPE mode. Check synth settings.
Notes cut off prematurely — you ran out of MPE channels (more than 15 held at once). Rare in real use.
No pressure response — enable aftertouch response on your synth, and confirm MPE is on in Mobile MIDI.