Isolating bassline

I have this song I want to remix. For the intro, there’s this little instrumental guitar passage that plays by itself - no other instruments at all. Later on, this guitar passage is repeated exactly the same way with a little bassline going under it. I want to isolate this bassline. I figured I could do something like that trick of removing vocals from a song, where you invert one channel, and that would remove the guitar part leaving just the bassline, but no luck. Anyone have any suggestions? Thanks.

Chances of the two guitar performances being exactly the same are almost zero, but you should be able to get at least a phaser effect if you got close.

Import the song and duplicate it. Command or Control-D

On the second track, drag-select and delete everything but the guitar solo. Push it underneath the combined performance with the Time Shift Tool (two sideways black arrows). Keep shifting the second track around bit at a time until you start to hear interference effects like flanging and phasing. That means you’re getting close.

If the original work was a downloaded MP3, you’re dead. MP3 compression would treat the combined performance like a different show and the two guitar segments would no longer be identical.

Koz

Okay, I’ve lined them up and I can hear a little bit of phasing. Now what?

An alternative to the inversion method (as described in the first post in this thread)
is the spectral subtraction method which has the advantage that the tracks do not have to be perfectly in-sync.
A free spectral subtraction plugin is available called Kn0ck0ut, (windows only). No phasing, but does introduce digital artifacts.

Just gave that Knockout yoke a try, I’m getting some interesting results with it. Thank you so much!