Invented by Lev Sergeyevich Termen (Leon Theremin), the Theremin is a unique electronic musical instrument that is played without any physical contact from the performer. It consists of two metal antennas that sense the relative position of the player's hands. One hand controls the frequency (pitch) by moving toward or away from a vertical antenna, while the other hand controls the amplitude (volume) near a horizontal loop antenna. The signals from the antennas are processed to create a haunting, ethereal sound often associated with early science fiction films and experimental music. It was one of the first electronic instruments and laid the groundwork for future synthesizers. Playing it requires incredible precision and 'aerial' muscle memory, as there are no frets or keys to guide the musician. Its use in 'The Day the Earth Stood Still' and the Beach Boys' 'Good Vibrations' (via a similar electro-theremin) cemented its place in pop culture history.