Editing Automatic double tracking (section)

==Invention==
ADT was invented specially for the Beatles<ref name="Martin pg.155">Martin pg.155</ref> during the spring of 1966 by [[Ken Townsend]], a recording engineer employed at [[EMI]]'s Abbey Road Studios,<ref name="Martin pg.155"/> mainly at the request of [[John Lennon]], who despised the tedium of double tracking during sessions and regularly expressed a desire for a technical alternative.<ref name=Lewisohn>Lewisohn, Mark, [[The Complete Beatles Recording Sessions]], Hamlyn (division of Octopus Publishing Group) for [[EMI]], 1988, p. 70, {{ISBN|0-681-03189-1}}.</ref>

Townsend came up with a system using tape delay, {{citation needed span|date=August 2023|after similar principles already in place for echoes applied via tape during a song mixdown}}. Townsend's system added a second tape recorder to the regular setup. When mixing a song, its vocal track was routed from the recording head of the multitrack tape, located before the playback head, and fed to the record head of the second tape recorder. An oscillator was used to vary the speed of the second machine, providing variation in delay and pitch depending on the change in the second machine speed. This signal was then routed from the playback head of the second machine to a separate channel on the mixer. This allowed the vocal delayed by a few milliseconds to be combined with the normal vocal, creating the double-tracked effect.<ref name="pedersen19">{{cite book |last1=Pedersen |first1=Karl |last2=Grimshaw-Aagaard |first2=Mark |title=The recording, mixing, and mastering reference handbook |date=2019 |publisher=Oxford University Press |location=New York, NY |isbn=9780190686635 |pages=9 |url=https://books.google.com/books?id=y9B2DwAAQBAJ&dq=Automatic+double+tracking&pg=PA9}}</ref>