The principles of beat frequency or heterodyning oscillators were discovered by chance during the first decades of the twentieth century by radio engineers experimenting with radio vacuum tubes. Heterodyning effect is created by two high radio frequency sound waves of similar but varying frequency combining and creating a lower audible frequency, equal to the difference … Continue reading The ‘Theremin’ or ‘Thereminvox’. Leon (or Lev) Sergeivitch Termen, Russia. 1922