Mini theremin

The theremin is an electronic musical instrument controlled without physical contact by the performer. The theremin uses the heterodyne principle (combining or mixing two frequencies) to generate an audio signal. The instrument's pitch circuitry includes radio frequency oscillator. The frequency of the other oscillator is controlled by the performer's distance from the control antenna. The performer's hand acts as the grounded plate of a variable capacitor in an L-C (inductance-capacitance) circuit, which is part of the oscillator and determines its frequency.

The theremin was originally the product of Soviet government-sponsored research into proximity sensors. The instrument was invented by a young Russian physicist named Lev Sergeyevich Termen.