I've always found a "shake" is harder to accomplish well sitting down than it is standing up. Just can't get the optimum motion in it when my bottom is stuck in the chair. Then too, can't remember any music I've played where it was called for, only for an exercise in one of my college classes and having practiced it the night before sitting without much success, I stood and played it well enough that without comment the prof moved on to another student. Too, I got a 3.5 grade point from that prof. Don't really like the sound of it ever since.