After listening to A Hard Day's Night on Thursday, I figured out (at least an approximation) of the bass part for "I'll Be Back." I might have some of the rhythms wrong, and I might even be missing some notes, but it's at least pretty close. One thing I discovered while learning it is that McCartney includes an extra note at the beginning of the first verse. In all the other verses, there's just a descending line starting with an A note, but in that first verse, he drops down to an E before going back to the A and then doing that descent. The part before that just alternates between A and E, so I think he just got stuck doing that and missed his cue.
I referenced The Beatles Complete Chord Songbook for the chords, although I didn't play them exactly the way the book has them listed. I think it sort of combines the other parts to get chords. So if the rhythm guitar plays a B minor chord over which the lead guitar plays an A note, the book just combines those two things and says, "Play a B minor 7th."
I tried to figure out the lead guitar part for this a few weeks ago and didn't get anywhere, but then I got the whole thing this afternoon before I recorded this.
