Tape tricks
Arguably the most essential Beatles studio technique was Ken Townsend’s inspired method of duplicating a track and processing it to mimic a second performance. This was initially devised to save the time, effort and accuracy required when doubling a vocal part, but, it would indirectly open up a new world of sounds.
Townsend’s trick involved taking two signals from the Studer J37 tape machine while it played the original track: one from the conventional playhead, and another from the sync head (effectively a recording head with playback capabilities). However, rather than simply superimposing the identical sounds, ADT’s genius was in routing that additional signal to a second tape machine, Abbey Road’s familiar BTR2. There it was recorded and immediately played back, creating a fractional delay that could be fine-tuned against the original (typically by up to 40 milliseconds) to create the illusion of a second performance when mixed back in with the original signal.
Conceived in time for the Revolver sessions, ADT vocals are all over that 1966 album ( And Your Bird Can Sing, Doctor Robert, Eleanor Rigby…), and appear on every subsequent album, up to and including Abbey Road.
The Beatles were so taken with the ADT that they used it on various instruments, including brass and even handclaps. However, rather than simply doubling, this was usually to harness the psychedelic flanging effects that emerged as a brilliant by-product of the process…
Varispeed: flanging, chorusing and phasing
While ADT was designed to duplicate a signal, John Lennon affectionately dubbed it, “Ken’s flanger”, reflecting how the same technique spawned some stunning textural effects. The term ‘flanging’ relates to the impromptu method of physically slowing the tape in motion by manually pressing on the flange of the metal spool; the resulting changes in speed and frequency creating the ‘wooshing’ sounds that launched a thousand guitar pedals. However, the Beatles took a more elaborate approach in the form of the frequency control feature of the BTR2. While only minimal tape speed tweaking was needed to create a convincing second vocal through ADT, ‘playing’ this varispeed function manually, via the handle of an oscillator, brought various flanging sounds as well as the shimmering pitch effects we now call chorusing.
An extreme example appears on the White Album’s While My Guitar Gently Weeps, where the mournful tremor on Eric Clapton’s Les Paul lines is down to engineer Chris Thomas “wobbling the oscillator in the mix”, as Mark Lewisohn reports in The Complete Beatles
Recording Sessions (1988). Meanwhile, in their profound 2006 tome,
Recording The Beatles, studio experts Kevin Ryan and Brian Kehew distinguish the related effect of phasing. This involved reversing the polarity of one of the two signals, causing a characteristic ‘drop out’ effect as the sounds overlap, briefly cancelling each other out at a certain point in the flanging swirl. Examples include George’s guitar solo on the mono mix of
Fixing A Hole, Ringo’s drums on Blue Jay Way and John’s vocal on Across The Universe.