This Ableton Live tutorial covers MPE, MIDI Polyphonic Expression, a protocol that lets expressive controllers send per-note data like pitch bend, pressure, and slide instead of one blanket signal applied to every note you're playing. Inside Wavetable's MPE Modulation Matrix, you can route any of the four supported parameters, Velocity, Per-note Pitch bend, Slide, and Pressure, to shape the synth's sound in real time.
Adding a parameter to the matrix takes one click on the control you want to modulate within Wavetable's interface, then dragging up or down in the matching slot to set how much modulation is applied. A meter under each label lights up to confirm the modulation is actually active, so you can check your routing at a glance.
The core idea worth internalizing: MPE modulation works per note, not globally. Play a chord with an MPE controller and each note responds independently to how you bend, press, or slide it, which is what makes the technique genuinely expressive compared to standard MIDI, where modulation applies evenly across every note you're holding.