A technique that creates two tracks of a recorded signal using only one actual recording. Double tracking has been a common studio practice for many years, most often utilized to create a fuller, “fatter” sound on lead vocals. The technique was simple: the vocalist would record his or her part twice. When the two versions were played back together, the minor variations in pitch, inflection, and timing would result in a uniquely thicker sound.
In a technological advance attributed to recording engineer Ken Townshend during a Beatles session, a recorded vocal track was re-recorded onto a separate machine that had been modified with a variable oscillator, causing the tape speed (and therefore the pitch) to fluctuate slightly up and down. This modulated signal was then fed back into the first machine to be combined with the original signal, emulating a double-tracked vocal. This technique was also widely used on guitar and other instrumental tracks.