A Theramin or Theremin is an electronic instrument played by waving your hands near a couple of antennae. It detects a capacitance effect between one antenna and hand to control volume, and between the other antenna and hand to control pitch. An early synthesiser.

Think of the incidental music from The Forbidden Planet if you want to know what it sounds like.

Or go to:

http://www.amazon.com/exec/obidos/tg/detail/-/B00000J8RP/103-4864267-8771018?v=glancehttp://www.amazon.com/exec/obidos/tg...67-8771018?v=g lance

go down to the Listen to samples section and click on the play links.