Very clever ideas here... The self-osc filter with velocity/pressure mod works great. But there were other ideas relating to LFO frequencies which I imagine works well too, along a different perceptual dimension.
... reminds me of a question we used to pose to beginning physics students - you are given a ball of string, a stopwatch, and a barometer. You job is to go to the top of the Empire State building and determine its height using only those things. (There is no single correct answer...)