Here's another cool youtube video clip of someone playing a Moog Etherwave Plus Theremin:
https://www.youtube.com/watch?v=ypFrVdEEiG4
The Theremin is one of the oldest electronic musical instruments known to man, it was invented by a Russian Physicist named Lev Termen in the late 1920's, as you can see in the video clip the Theremin is an electronic musical instrument that you can play without physically touching the instrument, it has two antennae attached to it, one which is positioned vertically and is the pitch antenna, the other is positioned horizontally and is the volume antenna, the pitch of the sound produced by the Theremin is controlled by positioning your hand closer to or further away from the pitch antenna, the closer your hand is in relation to the pitch antenna the higher the pitch of the sound produced, to control the loudness of the sound produced by the Theremin you move your other hand closer to or further away from the volume antenna, the closer your hand is to the volume antenna the softer the sound produced by the Theremin, you can get some very musical sounds out of the Theremin, you can also get spooky and weird sounds too.
I actually have a Theremin I built from a kit of parts I bought from Jaycar Electronics.