Watch the Sharp Stop online guitar lesson by Jeff McErlain from Play in the Style of Billy Gibbons
This is a really sweet lick, as Billy is using the b5 of the blues scale and bending it up a half-step up to the natural 5th. In typical fashion he is doing this in the context of a double-stop with the higher note being a Bb, which is the b7 of the scale. The background is chugging away on a C power chord and that leaves the harmony to be somewhat ambiguous. Power chords do not contain a third so the chord could be seen as either major or minor, depending on what notes we play. By adding in the b7 we are applying a Cm7 or C7 chord which is really common in a rock 'n roll context. Once again this is a great example of Billy's use of a double-stop to create dissonance to add tension. By bending the b5 up to the natural 5 and fretting the b7 on top we are hitting chord tones yet still leaving the ambiguity of the harmony. That all sounds kind of fancy doesn't it? At its heart it's just a cool dirty sounding lick. Another guy who I have heard play very similar ideas was the late, great Roy Buchanan. I do not know this for a fact, but I do know that Jeff Beck was heavily influenced by Roy's playing; one can only assume Billy was a fan as well.