The summer in question was back in 1969, the same summer as another festival in Woodstock, New York.
So why did that event become so famous, while the other was forgotten? That's just one of the intriguing questions explored in the new documentary now streaming on Hulu.
"Summer of Soul" is one of the best movies I have seen anywhere this year, and it offers a record of the Harlem Cultural Festival that ran for a few years in the late 1960s.
It's a music movie, but also a vivid portrait of a world in transition.
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Half a century has not diminished the power of what happened when history hit a pivot point. The music was the best of two different eras, the torch passed from one generation to another onstage.
In all, there were six weekends of major artists in the summer of '69. But as the name suggests, the Harlem Cultural Festival was about a lot more than music.
1969 brought about changes in the Black community, as riots had erupted the previous year following the assassination of the Reverend Martin Luther King, Jr.
"It was a crazy, crazy, crazy period," remembered one who attended the shows. "We needed something to reach out and touch us. We needed that music."
On June 19, some of those who had been there half a century ago returned to the festival site, now known as Marcus Garvey Park, for a showing of the documentary.
"It's about American culture, it's about American history," Marilyn McCoo said. "It's about what we all share, if we just look at it that way."
McCoo and her husband Billy Davis Jr. performed as part of the 5th Dimension, and a fan who saw them as a child was reunited with the couple at the premiere.
"It was just electric," Musa Jackson said. "It was a day where we just got to be with each other."
It was all recorded on video, and those tapes sat in a basement for decades until Questlove had them restored to create his first movie.
"This was much more than my directorial debut," he said. "This was much chance to correct history, and that's, that's so important."
"Summer of Soul" streams on Hulu, owned by the same parent company as this ABC station.
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The Woodstock festival in the town of Bethel captured the imagination of an entire generation, but events shown in in this film had largely been forgotten -- except by me.
The late Courtney Calendar, who helped to organize the Harlem Cultural Festival, was an early mentor of mine and hired me at WNET/Thirteen. So I came up in this business hearing all about the Summer of Soul.
Calendar was Deputy Commissioner of Cultural Affairs for the New York City Department of Parks at the time. He died of cancer in 1983 at the age of just 46.
A park in Harlem is named in his honor, and this new movie would have pleased him so much.