The bass line is a big part of FBI the more you listen to it.
I always thought the bass line went dum dum - dah dah dah - dum , yet the sheet music I have seen, seems to put it at doing dum dum, dum dum. etc .Unless there is an extra guitar line in there reinforcing the bass line and playing some extra notes ?
The bass is right up front in the mix which is unusual and more in middle than at sides. I would say it had been treated with llimiting too as is often the case with bass recording to tame transients.. The rhythm guitar sits behind the bass adding to the sound , but not anywhere near as loud as the bass. I think the bass line and the way it is recorded, is what gives FBI its sound mix. Still fantastic after all these years.