At least for sax, the hand positions don't vary a lot.  It's mostly fingers up and down.  For a piano, the whole arm moves, and different fingers are used on different notes depending on whether it is easier to cross over or to shift your hand.  Guitar and violin bring in another aspect, as with those there are alternate fingerings to most single notes.  Drums really bring out the ballistic problem; the drummer's arm must start moving long before the crash cymbal arrives in the music.  Animating a player on an instrument is a challenge indeed.