"Back in the U.S.S.R."
The White Album sessions were tense and scattered overall: Yoko Ono's presence in the studio became a distraction for everyone not named John; meanwhile, longtime engineer Geoff Emerick, frustrated by the band's squabbling, quit midway through. But the recording of McCartney's Beach Boys homage "Back in the U.S.S.R." was especially complicated since Ringo Starr had temporarily quit the group, leaving the remaining trio to pick up the slack. Both Harrison and Lennon overdubbed additional bass to flesh out a composite track; they also contributed extra drums, with McCartney's tense kit work mixed loudest amidst the "ooh-ohh" harmonies.
You can hear the band attempting to emulate Ringo's signature tumbling fills, but the same sophisticated spark just isn't there. Ringo has always taken a lot of flak for being the Beatles' weakest link, but "Back in the U.S.S.R." proved just how important he was — ironically, through his absence. The drummer returned to the studio weeks later, finding his kit decorated with flowers.