So, I was watching the "Shine a Light" movie this weekend (it was ok, and the cinematography was the best I've ever seen in a concert movie), and the first tune the Stones do is Jumpin Jack Flash. Keef kicks it off with a capo at the IV fret, and it's clear he's in some sort of open tuning (he keeps doing the exaggerated "look ma, no hands" thing). Makes sense that he's playing in open G, right, since the tune is in B? But then I saw somewhere where he said in an interview that he played it in open E or D (same relationships, just tuned down). So what do you use? How do you play the signature riff?