In the Summer of 1969, just 100 miles south of Woodstock, The Harlem Cultural Festival took place in Mount Morris Park (now Marcus Garvey Park). The footage of this epic celebration of Black history and culture sat in a basement for 50 years, unseen and largely forgotten - until now.

The multi-talented Ahmir "Questlove" Thompson, in his filmmaking debut, has retrieved this joyous cultural phenomenon, creating a powerful and transporting record of the event, which features never-before-seen performances by Stevie Wonder, Nina Simone, Sly and the Family Stone, Gladys Knight and the Pips, Mahalia Jackson, B.B. King and many more.