Edited sentence: " because Starr had left the group during the period when the song was being recorded.According to Mark Lewisohn's book The Complete Beatles Chronicle, McCartney, not Starr, played drums on "Back in the U.As of 2008, the actual musician/instrument lineup on the track remains disputed.Lewisohn also reports that, in the case of "Dear Prudence," also recorded during Starr's absence, the three remaining Beatles each made contributions on bass and drums, with the result that those parts may be composite tracks played by Lennon, McCartney and/or Harrison