MRC and feet. Granted, there's no intricate footwork such as on an organ, but we need to coordinate both feet, and we develop a very fine control of pressure in the right foot.
Absolutely. I'd add an additional important element: the synergy and coordination of all the elements listed, and the ability to rapidly shuttle among them.
MRC To me, the most important sense that is not much used is the sense of balance.
Another one that matters to me. If we don't have that sense, as we learn to play across the whole keyboard as well as pedaling, we don't fall off the bench but (if you're me) we'll stiffen and compensate in weird ways, which can restrict how we can move with ease.
