John Lennon sings a A on the line "She loves you and you know you should be glad." For a long time, I've assumed that this line is sung over a borrowed iv chord (C minor). In lieu of video footage possibly showing what the guitarists were playing, let's look at the possibilities for what's happening here:
1) Lennon is actually playing some voicing of an A half-diminished chord on the guitar during this line. If so, where might the idea of a half-diminished chord built on the supertonic, and used as a dominant prep chord, have come from?
2) Lennon is, in fact, playing a C minor chord, in which case the Beatles probably did not realize he was singing a non-chordal tone and this seemingly unique (?) harmonic phenomenon came about as a result.