I promised to say a bit more about how the theremin robot's software works.
It's built in Opcode's Max software running on a Mac. I found a freeware plugin for Max called fiddle, which does pitch tracking. I wired up the pitch monitor mod from the Etherwave manual, and sent the pitch monitor output into the Mac through a USB microphone. (The little white iBooks have no built-in microphone! I didn't know that when I bought one. Also, they can't run with the lid closed. Two reasons not to use an iBook for an audio robot's brain.)
So, through the pitch monitor and fiddle, the Max program always knows the theremin's output pitch, and the program controls the positions of the robot's arms, so you have everything you need for a closed feedback loop. Only, I didn't do it that way, because that would have taken more thought. I used an open loop system, where the robot goes through a calibration stage, and then plays freely without monitoring the accuracy of its output. During calibration, Lev moves its pitch arm slowly through its entire range, and memorizes the pitch it gets for each possible position of the arm. I found that the calibration was good for about an hour or until someone bumped into the theremin, which happened a lot with several thousand people trooping through the gallery. After an hour, changes in temperature and humidity were enough to throw the calibration off and I'd do it again.
Once the thing is calibrated, it's ready to take commands from the MIDI input. Each key on the keyboard is mapped to a pitch in the diatonic scale, and then the software hunts for the closest match in the calibration table. Because of the pitch arm's control limitations, the actual pitches played on the theremin were up to about 1% off from their correct values, even under ideal conditions. A semitone is about 6% (google says 1.05946309), so a 1% error was enough to make Lev sound quaint and sloppy, but not enough to sound totally wrong.
On top of the inherent pitch inaccuracies, the little pitch arm would vibrate as it snapped into place, and the entire assembly would gently rock back and forth because it wasn't completely solid. These gave Lev a nice sort of vibrato effect. On the whole, it sounded old-fashioned, like a soprano from the early 20th c. played on a worn out gramophone.
Jason, the poster is a hand-painted circus-style banner, 4 x 5 feet. I suppose it would be possible to make photographic copies...
