The final touch was added to the Sgt Pepper's Lonely Hearts Club Band during this session: the gibberish sounds which filled the run-out groove of the vinyl record.
First of all, however, 11 mono mixes of George Harrison's Only A Northern Song were made. Two four-track tapes had been filled: one with organ, bass guitar, trumpet, glockenspiel and drums, and another with organ, vocals and other assorted noises.
Two tape machines therefore needed to be synchronised, a process that had previously been used during the recording of A Day In The Life.
Once the mixes were complete, attention returned to Sgt Pepper. The Beatles stood at the studio microphone and babbled nonsense on each track of a two-track tape, which was subsequently cut up and re-edited with some parts reversed.
On 21 April everyone in the studio recorded the run-on spiral for the album, about two seconds’ worth of sound. It was a triple session - three three-hour sessions - which ended around 4am. The Beatles stood around two microphones muttering, singing snatches of songs and yelling for what seemed like hours, with the rest of us standing round them, joining in. Mal carried in cases of Coke and bottles of Scotch. Ringo was out of it. ‘I’m so stoned,’ he said, ‘I think I’m going to fall over!’ As he slowly toppled, Mal [Evans] caught him and popped him neatly in a chair without a murmur. In the control room no one seemed to notice. A loop was made from the tape of the muttering and was mixed, but not without some altercation between John and the tape operator.
In The Sixties
The album was cut by Harry Moss, and required several attempts before the sound appeared precisely in the run-out groove. The intention was for the sound to loop and be played ad infinitum, preceded by a 15 kilocycle pitch intended for dogs.
I was told by chaps who'd been in the business a long time that cutting things into the run-out grooves was an old idea that they used to do on 78s. Cutting Sgt Pepper was not too difficult except that because we couldn't play the masters I had to wait for white label pressings before I could hear whether or not I'd cut the concentric groove successfully, These were the things which, at the time, I used to swear about! It was George Martin who first asked me to do it. I replied, 'It's gonna be bloody awkward, George, but I'll give it a go!'
The Complete Beatles Recording Sessions, Mark Lewisohn
Neither the test tone nor the loop of gibberish - known as Edit for LP End on the tape box - was used on the first North American pressings of Sgt Pepper's Lonely Hearts Club Band. It was eventually issued as part of the Rarities compilation, with the title Sgt Pepper Inner Groove.