Here is the “new” Beatles song – a demo written by John Lennon, then picked up and produced by McCartney, Harrison and Starr. With lyrics added by McCartney, just as he might have done in the old days, when they frequently wrote the middle 8 for the other guy’s song. It’s all in the video – Penny Lane, the pretty lass is selling poppies from a tray, the cavern, the paperback writer, etc.
And then there is this version of Something, performed by Harrison in the 1990’s. Note how he has taken the guitar intro and changed it all around into a rather sweet bluesy feel. There is always the need to rewrite and improve.