Black Wax is an ecstatically free-associative portrait of blues poet Gil Scott-Heron. Though his music stretches back to the late ’60s—ingeniously mixing funk, jazz, and spoken word on classic tracks like “The Revolution Will Not Be Televised”—Scott-Heron’s commentaries on American values and racial injustice remain trenchant today. Here, veteran music documentarian Robert Mugge (Sun Ra: A Joyful Noise) lets Scott-Heron’s timeless themes take center stage.