1. One of several single-frequency signals at the beginning of a tape reel at the magnetic reference level that will be used to record the program.
  2. Any single-frequency signal or sound.
  3. The sound quality of an instrument’s sound relative to the amount of energy present at different frequencies.
  4. In some synthesizers, a term meaning the audio signal that will be put out by the unit which would be similar to the sound of an instrument.