Anyone remotely into science fiction has heard the sound of a Theremin at least once, from its use in most 50’s movie to a variety of later Star Trek and Doctor Who sounds. It has been the sound of the future since its creator Leon Theremin unveiled it in 1928.
Before I explain, what it is it is important you see what it looks like in use. For reference the Theremin playing begins at 1:00.
So how does this machine work? Well, this connects back to our unit on capacitance. The human body has a natural capacitance, so when it moves into an electric field it can disturb it. In a Theremin an electromagnetic field is created by a radio frequency oscillating circuit. The two terminals are connected to two different circuits. The circuit connected to the vertical antenna is connected to a variable oscillator which can produce a range of frequencies, making the player’s movement in the vertical plane control the pitch of the instrument. The horizontal terminal has a fixed oscillator which generates waves at a constant frequency. A hand in the horizontal plane controls the volume of the output. When these two signals are “mixed” and amplified, the result is the haunting pitch you hear above.
This instrument paved the way for the electronic era of instruments to come, so looking back, it is always important we acknowledge our roots.
As always thanks for reading! - ThePeculiarParticle