There is a sensor right on the drum skin. You can control the intensity of each drum depending on how you hit it. And colors are mixed on the fly from the values coming from each drum.

Sensors are connected to arduino, arduino to max and max to DMX through lanbox. These were test drums, they looked and sounded bad so I didn't use the audio from the video.

Ahh.
nice :)

Now we are moving towards just using Arduino with an ethernet shield talking to the lanbox so we don't use a computer at all and cut any possible lag.