Heres a pic of an a100 system with the Theremin controllers installed, each antenna is 100 bucks, you can assign any parameters of the sound to be controlled by moving your hands between the two antennas on x-y axis'
This pic is from their site.
neat huh.... great for wrist work outs!
hehehe
<img src=http://doepfer.com/a100ther.gif>