In 1951, Bernard Herrmann changed the sound of science fiction forever by using the Theremin in 'The Day the Earth Stood Still.' The Theremin is unique because it is played without physical contact—the musician moves their hands near two antennas to control pitch and volume. Herrmann used two Theremins to create the eerie, oscillating sound that represented the alien Klaatu. This was a radical departure from the romantic, orchestral scores of the time. The instrument’s wavering, high-pitched vibrato became the definitive sound of 'aliens' for decades. It helped establish the Theremin as a cinematic legend in its own right, proving that electronic instruments could carry as much emotional weight as a live orchestra. Its legacy can still be heard in the soundtracks of modern legends like Tim Burton.