MPE / Note Expression
Returns per-note pressure or aftertouch in the range 0.0 to 1.0. Use it when you want one held note to open up, brighten, distort, or otherwise react independently from other notes.
Defaults to 0.0 until the corresponding note expression event arrives from the host.
sin(X)*(0.2+0.8*pressure())
This function only changes the sound if your formula actually uses pressure(). In an MPE controller such as a Seaboard, each active note can carry its own pressure value.