HOW IS PAUL MCCARTNEY SO GOOD?

TWO BASSES ON FIXING A HOLE?

What's happening in the bass part on the Beatles song "Fixing a Hole?" Why does it sometimes sound like there are two basses? Well...
Rob is playing a 1985 Rickenbacker 4003 through a SansAmp VT Bass Deluxe.
His bass is strung with LaBella flatwound strings.
Music and lyrics by John Lennon and Paul McCartney