A very good essay on McCartney and not only how he grew, changed, and even became a bass player in the first place, but it analysis the songs, albums and the players and points out, what may sound run of the mill today, how it was revolutionary when Paul did it.
Full of great insight too. For instance, I think most of us, as well as the casual fan, think Paul became the bass player when Stu left because he was the 'third" guitar player. As Paul says here, when Stu left John had just bought a new Rick guitar and wasn't going to switch, George said no way and Paul didn't even own a guitar, he was playing piano mostly. So when they turned to him for the bass duties, he didn't have an argument against.
This isn't only a trip down memory lane but is filled with great lessons for anybody aspiring to play bass. Enjoy.
http://abbeyrd.best.vwh.net/paulbass.htm