“Do you wanna go way down in the alley?” Buddy Guy asks the audience at Boston’s Nightstage in 1986. “Do you really want to hear some blues you don’t get anymore? Well, watch this shit!” With that, he turns the microphone over to his co-bandleader Junior Wells, who hushes the sextet to a mere murmur. He sings Muddy Waters’ “She Moves Me” in a baritone as quietly ominous as the fills from his own harmonica and from Guy’s guitar.