For this session only it had the working title In The Life Of..., and the group began by rehearsing with John Lennon on piano, Paul McCartney playing an organ, George Harrison on an acoustic guitar and Ringo Starr playing congas. These rehearsals were recorded but later wiped.
For the four proper takes, Lennon sang a guide vocal onto track four while his acoustic guitar, McCartney's piano, Harrison's maracas and Starr's congas were taped together onto track one. Onto take four Lennon added two vocal overdubs onto tracks two and three, with some piano licks by McCartney on the latter.
There was so much echo on A Day In The Life. We'd send a feed from John's vocal mic into a mono tape machine and then tape the output - because they had separate record and replay heads - and then feed that back in again. Then we'd turn up the record level until it started to feed back on itself and give a twittery sort of vocal sound. John was hearing that echo in his cans as he was singing. It wasn't put on after. He used his own echo as a rhythmic feel for many of the songs he sang, phrasing his voice around the echo in his cans.
The Complete Beatles Recording Sessions, Mark Lewisohn
The Beatles were unsure what they wanted to fill the two bridge sections with, so had Mal Evans count out 24 bars. At the end of the first sequence an alarm clock was set off. The clock later provided the perfect introduction to McCartney's vocal passage.