Oddly enough, I've just been doing some (Internet) reading on Leon Theremin, aka Lev Termen. There's a decent bio at http://www.obsolete.com/120_years/machines/theremin/ that lists many of his less-well-known inventions (including the first electronic eavesdropping device). Also interesting is his kidnapping and subsequent time incarcerated in a Siberian labour camp with (among others) Sergei Korolyov, former Soviet space engineer and chief designer for many of their early space missions.

the Theremin was the intrument used in the Beach Boy's Good Vibrations. it makes a single tone, and the operator of the theremin can adjust volume and tone by raising or lowering his or her hand in the field created by the theremin. there are no moving parts and you don't touch the instrument to play it. a wavering sound can be created by rapidly moving your hand up and down a slight distance. Theremins can still be purchased.