FWIW, just to clarify in case you do write about it. Aftertouch is not necessarily used for pitch change (though it’s a great use of it as RonW suggested and could indeed be used for microtonal stuff that given the quality/complexity of today’s sample engines could probably fool pretty much anyone). It’s just another control message and it can be assigned/used for anything. There is also a channel version of the control versus the single note message.