You can treat it like a feedback system, sitting back and letting it function. You can also take an active role, bowing, re-tuning, and striking. I sometimes bring it to group-improvisation situations.
It consists of a tom drum, with a transducer-exciter fixed to one drum head and a microphone on the other drum head. Inserted into this feedback loop is a Max patch that, among other things, modulates a low-pass filter applied to the microphone signal before it is fed back to the transducer.