Summer of Soul includes some wonderful retrospective testimonials from performers, including Gladys Knight, Mavis Staples, and Stevie Wonder. But even more affecting are present-day interviews with audience members, many of whom were adolescents at the time and seem profoundly moved by the opportunity to revisit such a formative musical experience. Their recollections are affecting, charming, and frequently funny—one attendee recalls his shock at discovering that Greg Errico, the monstrously funky drummer of Sly and the Family Stone, was a long-haired white guy.

But the real attraction is the music, as it should be. There is a remarkable amount of stylistic diversity on display, including pop (David Ruffin, Gladys Knight and the Pips), jazz (Sonny Sharrock, Max Roach and Abbey Lincoln), blues (B.B. King), boogaloo (Mongo Santamaria, Ray Barretto). There’s also a generous helping of gospel, a programming decision that likely doubled as a canny olive branch to an older demographic of Harlemites who might otherwise have bristled at the idea of rock stars like Sly Stone and the Fifth Dimension (and their legions of young fans) intruding onto their Sunday afternoons.

And of course there are the performances themselves, some of which capture absolutely legendary artists at fascinating points in their career. Mahalia Jackson and Mavis Staples, representing two generations of musical royalty, duet on “Take My Hand, Precious Lord,” notably the late Martin Luther King Jr.’s favorite gospel song. A 19-year-old Stevie Wonder performs “Shoo-Be-Doo-Be-Doo-Da-Day” and takes a blistering clavinet solo through a wah-wah pedal, a preview of what would soon become one of the signature sounds of Wonder’s 1970s reign. And if Summer of Soul finds Wonder on the cusp of his imperial period, it finds Sly in the full flower of his own, delivering jaw-dropping renditions of “Sing a Simple Song” and “I Want to Take You Higher” with the irresistible force of the Family Stone behind him.

One of the thorny truths about the ’60s’ most “iconic” music festivals is that they were often overwhelmingly white lineups and conceived as such. For all of the utopian peace-and-love bromides that have long clung to Woodstock, Sly and the Family Stone was the only act on the bill with any significant presence on Billboard’s R&B charts, and the festival’s remote rural location made it difficult to access for urban audiences. The extent to which these choices were deliberately exclusionary has been a subject of debate over the years, but it’s clear that Woodstock’s (and Altamont’s, and to a lesser degree Monterey’s) vision of the ideal hippie music enthusiast was a white one, a vision that was also often reflected in the way these festivals were filmed.