Hey Jim, not at all mate. That is simply a drill to begin to appreciate the inward activation of the aperture corners without the jaw elevating.

When playing in the Low C and above range, the gap is about the same as if you were to put your little finger between your teeth. Lightly bite on your little finger at the nail and get a sense of that.

The jaw will go lower if you go down in pitch from there.

Have you been across to the support network yet to see the previous Sunday Sessions and Teaching Tuesdays. They are very valuable.

Cheers
Greg