The Theremin…from Wikipedia:
The theremin is one of the earliest electronic musical instruments, and the first musical instrument played without being touched (originally pronounced it is also known as an aetherphone. It was invented by Russian Leon Theremin in 1919. The controlling section usually consists of two metal antennae which sense the position of the player’s hands and control radio frequency oscillator(s) for frequency with one hand, and volume with the other. The electric signals signals from the theremin are amplified and sent to a loudspeaker. The theremin is an electrophone, a subset of the quintephone family.
To play, the player moves his or her hands around the antennas, controlling frequency (pitch) and amplitude (volume). The theremin is associated with an “eerie” sound, which has led to its use in movie soundtracks such as those in Spellbound, The Lost Weekend, and The Day the Earth Stood Still. Theremins are also used in art music (especially avant-garde and 20th century “new music“) and in popular music genres such as rock.
Pretty cool eh?