This is what Sir Paul recently had this to say: "When I kind of got into songwriting, I realized how well structured these songs were, and I think I took a lot of my lessons from them," explained the star, "I always thought artists like Fred Astaire were very cool. Writers like Harold Arlen, Cole Porter, all of those guys – I just thought the songs were magical. And then, as I got to be a songwriter I thought it's beautiful, the way they made those songs."
Well, quite, though early Beatles , when they left the path of early rock and roll, seemed more likely to sing showtunes like "Till There was You" or novelty hits like "Besame Mucho".
Still, if Macca sez those are his roots, who are we to disagree. In the new Lennon bio much is made of Lennon and McCartney hanging out at the NEMS record store (the one Epstein owned) and figuring out the chords and the lyric to new hits and taking it with them back to the cavern.