Although none of them knew it at the time, 1 August 1969 was a significant date for The Beatles: it marked the final time that all four members began recording a song together.
It took 23 attempts to perfect, and take 16 was chosen as the best. George Martin played a Baldwin electric harpsichord, Lennon was on electric guitar, Paul McCartney played bass and Ringo Starr kept time by tapping a simple rhythm on the hi-hat.
Having done the backing track, John, Paul and George sang the harmony. Then we overlaid it twice more, making nine-part harmony altogether, three voices recorded three times. I was literally telling them what notes to sing.
The Complete Beatles Recording Sessions, Mark Lewisohn