This guy explains how to sit on the piano bench correctly. He includes a discussion and demonstration of the correct distance to sit from the piano and the height of the bench. As he says, sitting correctly will help us play easier and avoid injury.
You've got to learn your instrument. Then, you practice, practice, practice. And then, when you finally get up there on the bandstand, forget all that and just wail.
I'm a professional pianist and music educator in West Toronto Ontario. I'm also a devoted percussionist and drum teacher.