Ive been learning some Beatles basslines recently and its certainly a tough job as Paul is such a great bass player.
But I just wonder whether what is on the final recordings is what Paul always intended to play in specific parts of the song?
Sometimes it just feels like he's "making it up as he goes along" as no two sections in most of the Beatles songs has the same bassline played EXACTLY the same twice from verse to verse to chorus to chorus (extra notes here and there, different rhythms etc). This makes it incredibly hard to remember the parts. This is even so in some of the really, really early releases.
Perhaps to none musicians listening to Beatles stuff its not even noticeable (after all not many people listen to much else in a song except the lyrics and main melody).
I'm not having a go at Paul, nor at any Beatles fans and I know this is what makes a great bass player, but I do have to question whether different takes during recordings of the same song had the exact same bassline note for note as on the finished release.
I don't suppose it was done that way on purpose - as a musician you do tend to play things slightly differently each time you play a song. Even if you are really concentrating on playing a part in exactly the same way each time, it is a difficult thing to do. And on a lot of the early songs, they probably hadn't rehearsed them a lot of times before the recording session, so they were still working out their parts during the recording process.
You may find that it is on the cover versions that Paul (and the others) show more consistency, because these are songs that they had been playing over and over in concert for years and years and the parts will have been ingrained in their brains.
Also, in the early days of The Beatles especially, when the whole band was usually recording the backing track instruments together, it would have been difficult to capture a "perfect" performance from every member of the band, so if you listen to Beatles records you can often hear slight "mistakes" in there - the rest of the take will have been OK to use, so they let the occasional error pass, just so they didn't have to keep doing take after take after take.