ON THIS NIGHT IN 1967, The Beatles DELIBERATELY BROKE EVERY ORCHESTRAL RULE TO CREATE 24 BARS THAT CHANGED MUSIC HISTORY. Paul McCartney stood in EMI Studio One conducting a 40-piece orchestra instructed not to play together, not to listen to each other, sliding from the lowest possible notes to the highest in rising chaos, recorded repeatedly until it sounded like 200 musicians, while fake noses, paper glasses and rolling cameras turned a formal session into something dangerously unrepeatable. And almost no one outside that room was ever meant to see how close it came to going completely off the rails.

“What I did there was to write, at the beginning of the 24 bars, the lowest possible note for each of the instruments in the orchestra,” George Martin would explain. “At the end of the 24 bars, I wrote the highest note each instrument could reach that was near a chord of E major. Then I put a squiggly line right through the 24 bars, with reference points to tell them roughly what note they should have reached during each bar.

“The musicians also had instructions to slide as gracefully as possible between one note and the next. In the case of the stringed instruments, that was a matter of sliding their fingers up the strings. With keyed instruments, like clarinet and oboe, they obviously had to move their fingers from key to key as they went up, but they were asked to ‘lip’ the changes as much as possible too.

“I marked the music ‘pianissimo’ at the beginning and ‘fortissimo’ at the end. Everyone was to start as quietly as possible, almost inaudibly, and end in a (metaphorically) lung-bursting tumult. And in addition to this extraordinary of musical gymnastics, I told them that they were to disobey the most fundamental rule of the orchestra. They were not to listen to their neighbours.

“A well-schooled orchestra plays, ideally, like one man, following the leader. I emphasised that this was exactly what they must not do. I told them ‘I want everyone to be individual. It’s every man for himself. Don’t listen to the fellow next to you. If he’s a third away from you, and you think he’s going too fast, let him go. Just do your own slide up, your own way.’ Needless to say, they were amazed. They had certainly never been told that before.”

The orchestra was recorded onto a separate reel of tape that, thanks to Ken Townsend and the EMI technical team figuring out how to run two four-track machines together, ran parallel to The Beatles’ previously-recorded instruments and vocals – allowing for said orchestra to be recorded five times and sound like 200 session musicians.

“After one of the rehearsals I went into the control room to consult Geoff Emerick,” The Beatles’ producer continued. “When I went back into the studio the sight was unbelievable. The orchestra leader, David McCallum, who used to be the leader of the Royal Philharmonic, was sitting there in a bright red false nose. He looked up at me through paper glasses. Eric Gruenberg, now a soloist and once leader of the BBC Symphony Orchestra, was playing happily away, his left hand perfectly normal on the strings of his violin, but his bow held in a giant gorilla’s paw. Every member of the orchestra had a funny had on above the evening dress, and the total effect was completely weird.”

Intending to produce a TV special about the making of the Sgt. Pepper, assistant Tony Bramwell oversaw the use of silent colour film to capture the evening’s proceedings.

“We handed out loaded 16mm cameras to invited guests including, among others, Mick and Marianne, and Mike Nesmith of The Monkees,” he’d recall. “They were shown what to press and told to film whatever they wanted. The BBC then banned the subsequent video. Not because of the content of the footage, but because the song itself had drug references.”

Here’s some of that footage…