Spring 1966, Abbey Road. John Lennon refused to manually double-track his vocals one more time. Ken Townsend, EMI engineer, wired a second tape machine into the playback path with an oscillator varying its speed — and built ADT (Artificial Double Tracking).
The wobble in that varispeed became flanging. Then chorus. Then every modern vocal effect.
The Beatles used it across Revolver. Lennon's impatience reshaped pop production.
— Townsend / Abbey Road, 1966
