Conversation so far:
Where were the abbey road rehearsals for the song, hey jude?
The Beatles first taped 25 takes of Hey Jude at EMI Studios in London over two nights, 29 and 30 July 1968, with George Martin producing. These served as rehearsals
Are there any other interesting aspects about the Hey Jude rehearsals besides them taking place at EMI Studios in London?
The 30 July rehearsals for the song, Hey Jude were filmed for a short documentary titled Music!, which was produced by the National Music Council of Great Britain.
Who did the Beatles rehearse Hey Jude with?
The film shows only three of the Beatles performing Hey Jude.

Question: why only 3 beatles?
Self-contained rewrite: why were there only 3 beatles performing Hey Jude during the rehearsal?