The Fifth Beatle...
For example, for Strawberry Fields John asked Martin for strings. And John choose which takes he liked best and Martin put together the song...
That's why we have things like this:

0:59
    Perhaps the most famous Beatles edit ever. In fact, it is actually two edits. The famous one is between take 7 and take 26. Take 7 was slower and a whole note lower in key. The two were edited together right between the words "cause I’m" and "going to". The lesser known edit occurs right before the words "Let me take you down". It’s also less noticeable (0:55.5) as a slight blip out in the Mellotron

The main edit (0:59) can be heard clearly by listening to the drums and Mellotron on the left channel. The drums go very dead, and the Mellotron stops. At the same time on the right, the orchestra appears from nowhere.

http://www.pootle.demon.co.uk/wgo.htm