MPE / Note Expression
Returns per-note pitch-expression, often the X axis of an MPE controller, in the range 0.0 to 1.0. This is useful for per-note pitch-related motion, timbral drift, or any formula movement tied to horizontal finger motion.
Defaults to 0.5 on note-on because tuning note expression is normalized and centered there.
sin(X*(0.9+0.2*glide()))
A centered resting value of 0.5 means you can treat left and right movement symmetrically around the middle. This function only affects sound when the formula uses glide().