THE THEREMIN

Invented by the Russian physicist Leon Theremin, the Theremin is the only instrument which is played without touching. The different frequencies and amplitudes of sound are produced by moving your hands near two antennae. This changes the capacitance (and thereby the resonant frequency) of the instrument's LC circuits because your hands act as the grounded plates of capacitors: if your hand moves closer to the the antenna, you are increasing the capacitance; move it further away and the capacitance reduces. Your body is effectively acting as a variable capacitor.
(remember that capacitance is inversely proportional to distance according to C=ε0εrA/d)
The weird and ethereal sound of the Theremin has been used in popular and classical music, and horror and sci-fi films.