What is the sound of no hands clapping

Mirabell just gave us the pre-show pep talk. I think it was a pep talk, since he seemed pretty jittery giving it.
"All right: it's time for the magic of the theatre to begin. Except for you, Fleance, you're just not working and I'll play your part. You just take a free branch and join the forest." Then he did the power circle that he claimed every show started with. It was more of a power rhomboid. Mirabell's out mingling with parents, teachers, unwary students, and the janitorial staff.