are you talking about this scene?
www.youtube.com/watch?v=mANbl6QX9ok (the clip can't be embedded).
Just over 3 minutes in, after the warped carnival / circus music? I'd bet good money it's a live Jimi Hendrix track slowed down, panned, and faded, just enough so they didn't have to pay for the rights. Though where the film didn't come out until almost a decade after Hendrix's passing it could just as easily be Eddie Hazel doing his best impression / improvising in a studio.