I have the luxury of listening to a couple of the first takes of the song when the Beatles are still rehearsing their parts individually. Here’s what I hear: George Harrison, playing his Rick 360/12, is playing a Dm11. From low to high that’s X00213. John Lennon is playing his Gibson Acoustic in a variation of G major 320033. Paul is playing octaves on his bass…D. Now George Martin is also filling in on the piano with I don’t know what. Ringo Starr is striking the snare with a quick bang. That’s the essense of the big sound you hear at the head of the song.