George Martin probably had more claim than anyone on Earth to the title of the Fifth Beatle.
He not only produced (almost) everything The Beatles recorded in their peerless eight-year recording career, but also played on oodles of it, and helped push the band further than anyone in pop with their joint studio experiments.
Less than impressed by a demo tape of the band sent by Brian Epstein, a sympathetic Martin agreed to give The Beatles – John Lennon, Paul McCartney, George Harrison and, at that time, Pete Best – an in-person tryout at Abbey Road.In the flesh, things didn't go any better. The not-yet Fab Four set up at Studio Two on June 6, 1962, and after some difficulties with McCartney's amp, eventually got going with a run through Consuelo Velazquez's 'Besame Mucho'.
Source: Mayer Nissim/goldradiouk.com