This robot drum arm comes from Georgia Tech, and was originally designed as a way to help a drummer who had lost an arm. (No, not the one from Def Leppard.) Here, the drum arm augments an existing drummer. While the user in question is wearing a headband with sensors, that part of the project isn't ready yet. Instead, the robot arm is drumming of its own accord, with some awareness of what the human is doing. It listens, and it plays along.