The Radiodrum[1] or radio-baton is a musical instrument played in three-dimensional space using two mallets (snare drum sticks with wires).
It was developed at Bell Labs in the 1980s (and patented),[2] originally to be a three-dimensional computer mouse.
The radiodrum works in a similar way to the theremin, which uses magnetic capacitance to locate the position of the drumsticks.
Max Mathews recognized its musical potential, mainly focusing on a conducting paradigm, and developed several other versions of it.
In addition to X, Y and Z, there is an output for the derivative of Z, which is used to detect changes of direction of the mallets, enabling fine control over snare-drum rolls and other nuanced percussive techniques.