In the summer of 1969, hundreds of thousands of fans flooded Harlem's Mount Morris Park to attend the Harlem Cultural Festival, which hosted the likes of Stevie Wonder, Nina Simone, Mahalia Jackson, and Sly And The Family Stone. Now, some of that footage is unearthed in a new documentary, directed by Questlove from The Roots, titled Summer of Soul (...Or, When the Revolution Could Not Be Televised).