This film would have brought the Harlem Renaissance and its luminaries to far greater prominence, during an era that was often neglectful of that movement’s heroes—and of new Black artists, too, as Greaves himself experienced. Shot in 1968 and completed in 1971, it was rejected by the Cannes Film Festival and never got distribution. In “Once Upon a Time in Harlem,” Greaves develops an approach to nonfiction that’s similarly inventive and thrilling, yet nonetheless straightforwardly informative. He filmed a series of interviews with some Harlem Renaissance notables and then held—and filmed—a party for a wider range of participants, at Duke Ellington’s home in Harlem. The footage was originally shot for a film about the Harlem Renaissance called “From These Roots,” which Greaves did complete, in 1974, but ended up making almost entirely with archival photographs.