rushed to find this
Let’s listen to a tape recording of sacred music – Tibetan monks or Gregorian singing. If you listen, you can hear how the voices merge, forming one pulsating tone.
This is one of the most interesting effects inherent in some musical instruments and a chorus of people singing in about the same key — the formation of beats. When voices or instruments converge in unison, the beats slow down, and when they diverge, they accelerate. Continue reading