I'm going to merge this topic with a topic by the same name we had a few years ago. This is a great topic for discussion.
Was this another first? Direct injecting the bass guitar into the mixer rather than go through amp and microphone. Ken Townsend (Beatle engineer) seemed to think so. It's hard of course to be sure if it hadn't been tried elsewhere but I wonder if there's any record of it being used for bass before this.
Moog, I think Paul used a Tone Bender inline with his bass amp to get the fuzz bass effect...
But, Moog, I'm pretty sure John plugged his Epiphone Casino directly into the mixer to get that distortion on Revolution...http://youtu.be/BGLGzRXY5BwD