tags: mus-407 early-electroacoustic-instruments

Heterodyne principle

The Heterodyne principle is a phenomenon that occurs when two [frequencies] are multiplied together, creating sum/difference tones.

Example usage in the [theremin]:

• two RF [oscillators]: one variable, one fixed at ~300 kHz
  • antenna & grounded performer act as capacitor
  • proximity to antenna alters output voltage
  • think like condenser mics with the capacitor plates
  • two oscillators are multiplied together, producing two tones at sum/difference frequencies (called heterodynes, heterodyne frequencies)
  • frequency of difference tone is within audible [spectrum]

Sources

• MUS 407 History of Electroacoustic Music: Early Instruments