Documentary captures historic 1972 Harlem gathering of Renaissance figures

• In 1972, filmmaker William Greaves organized a historic gathering in Harlem.
• The event brought together key figures of the Harlem Renaissance who hadn't seen each other in 50 years.
• The party took place in Duke Ellington's Harlem apartment.
• The documentary 'Once Upon a Time in Harlem' highlights this significant reunion.
• The gathering is considered one of the great parties of the 20th century.