Studio Three (control room), EMI Studios, Abbey Road
Producer: George Martin
Engineer: Norman Smith
The final day of studio work for With The Beatles involved the creation of a stereo mix of Money (That's What I Want).
The mix was made in a three-hour session beginning at 2.30pm, and was overseen by producer George Martin.
As so many overdubs had been added to the song, it was felt that further tape-to-tape copying would risk losing audio fidelity. To get around this, the stereo mix consisted of two separate mono mixes, one played through each left/right channel.

It fascinates me how George Martin achieved a stereo mix with center filled with vocals and handclaps!
My theory is that normally we would have instruments on the left & vocals on the right, but we have a piano overdub, so George and Norman pushed vocals to the center, leaving the space for the piano on the right.
All George Martin did was take his 2 mono mixes an put one In each channel causing vocals in the center.
Ok, but 2 mono mixes would cause 2 rhythm tracks played on both channels. The rhythm track is only on the left. My theory is that they put July 63 recording without the piano overdub and then they put 2nd track - vocals with September piano overdub, and put both recordings in sync.
Left - rhythm track
Center - vocals
Right - piano
Sorry, if it's confusing!