Let's think about speed: I think it's fair to say that Beethoven developed the notion of musical speed more explicitly than anyone else, specifically the direct connection between the very fast and the very slow. I am convinced that he responded to the vibration speed in slow tempos, of which most of us are entirely unaware.

One of my students is incredibly aware of that speed and, oddly, it slows down his superficial motor responses. It is an internal involvement which has required of me that I learn to hear and respect it. This is the student who plays a Beethoven sound more expressively than I can imagine doing myself. I am convinced that he responds to the piano in a manner comparable to Beethoven's, otherwise he could not intuitively find such a sound.

The sound defies theoretical identification or description much the way that piano sound defies electronic synthesis.