Realizing they sounded average at best, Macca wasn't surprised in 1962 when record label Decca refused to sign the band - who went on to become the biggest of all time.
In an interview with Xfm's Ian Camfield he said: "We obviously weren't that good. We were formulating it all.
"You wouldn't have thought we were that great. You'd have turned us down if you were a record company. And they did - Decca turned us down!"
Soon after Decca snubbed the Fab Four, producer George Martin signed them to EMI's Parlophone label and the band - prior to sticksman Ringo Starr's arrival - went on to play a 48-night residency in a Hamburg, Germany, club.
It was during this formative era that they honed their sound and learned the art of wowing crowds.
Macca said: "When we first went to Hamburg, and there'd be no-one in the club.
"You'd see a couple of students, maybe a guy and his girlfriend, and they'd look in a bit tentatively, look up at the price of the beer, see it was too much and start walking out.
"So we'd go, 'Come on, everybody, get back in here! It's all happening!'
"So we'd learned to attract an audience. After a few weeks, we'd be really packing those clubs.
"It taught us that game of how to win over an audience.
"We learned loads of songs, so by the time we got back to England, we had quite a big repertoire."