A guitarist I worked with for a period several years ago told me after years of playing, they downloaded (I believe it was) Audacity, and figured out how to make it record "what they hear" on their computer, and then used it to isolate a solo they wanted to learn.

We used to have little jam sessions and record them with this same method.

He would adjust a selection until it loops perfectly through the first part of the solo, and save it to a new track. Then the next solo section, and so on, until they had a track for each section.

Then they'd spend time on each section, letting it loop over and over, until they got it.

I haven't spoken to this person in a long time now - we used to have a lot of fun, he's moved on to be a studio musician for decently big acts, and he's based out of Toronto now. I've heard they're doing very well for themselves.

Cheers,
Deryk