It is probably the most famous – and argued about – opening chord in music history. It turns out that it’s not one chord, but a band – plus their Producer – all playing different ‘chords/notes’. I think these guys have it right (listen to audio clip at the end) – but they missed George Martin who added even more notes on a piano. As the clip says:
Electric 12 string (George H): F chord, but with G on top and bottom strings, plus C on the 2nd bottom string (B)
Bass (Paul) D note
Rhythm Guitar (John) D sus 4 (F# becomes G)
Listen to the magic sound, right near the end, when they play all 3 at once. What a beauty, no wonder they sound excited at having nailed it :
https://youtu.be/gwfH9oAiPH0
I’m also sure I read that George H says he repeats his opening F (+G +G +C) chord at the end, but plays each note; arpeggio style.