Hmm. I suppose you consider tapping on a desk, or rolling on bongos the equivalent of a sketch?

Absolutely. I can't say enough good things about drumming: literally every bit of music I hear can become a collaborative (well, Karaoke-style collaboration) piece of shared expression. The only limit is the degree to which I'm willing to annoy the people around me.

Ha, never thought of it that way but a lot of times you are sitting in class and think up something on your desk so I guess so