[header] How to make a theremin [title] Learn the essential components of the theremin. [step] A theremin is basically a box with two antennas, one of which controls the pitch of the instrument, the other of which controls the volume. These antennas create electromagnetic fields which are " played " by manipulating them with the hands. 
Coils of tight-pack wire act as oscillators, producing signals fed into the antennae. While it may seem like spooky magic, the fields are created by relatively straightforward circuitry.