Definition
Aftertouch is the pressure data a pad sends after the initial strike, while you keep holding it down. Channel aftertouch sends one combined pressure value for the whole controller.
Example
Press harder into a held pad and, with aftertouch mapped to a filter, the sound brightens; ease off and it darkens again. The expression happens entirely during the sustain of the note, after the hit has already triggered.
Why it matters
A pad strike is a single instant, but music often needs movement during a held sound. Aftertouch adds a continuous expressive dimension (vibrato, filter sweeps, swells) controlled by pressure, so a held pad can evolve instead of staying static and lifeless.
How to play or configure
Confirm your controller actually sends aftertouch, then map it to a parameter such as filter cutoff, modulation depth, or volume. Set the range so resting pressure does nothing and firm pressure reaches the musical maximum. Practise applying pressure smoothly; jerky pressure produces jerky modulation. Remember that channel aftertouch moves every held note at once.
Related terms
Further reading
MPC vs Maschine vs Push notes which pads support aftertouch.