But making the film didn't satisfy Belafonte.
"I could touch on everything, but I couldn't go in depth into many things," he says. "That's when a book appeared as a possibility."
That memoir, "Harry Belafonte: My Song," written with Michael Shnayerson, was released this week by Knopf.
It was only by accident that Belafonte ever rose to such prominence. Returning to New York after serving in World War II, he was working as a janitor's assistant when, as gratuity for an apartment repair job, he was given a ticket to a production at the American Negro Theatre in Harlem.
"It was an epiphany," he says, his eyes lighting up at the memory, "the people and stories and lights and magic."
Deliriously happy just to be working behind the scenes, he eventually got cast in a performing role: as a troubadour to link the scenes of a production of John Steinbeck's "Of Mice and Men."
He had never sung before, and even then didn't see himself as a singer: "I was acting," he says. But this acting role introduced him to folk, blues and calypso music, with their power to convey important stories. He set about to tap these music genres for a singing act.
It wasn't long before he was a household name, a mainstream star, a matinee idol recognized around the world.
More than a half-century later, he remains a handsome, princely presence, though clearly comfortable enough to poke fun at himself: When he learned that "Sing Your Song" would premiere at the 2011 Sundance Film Festival, "I understood what that meant: big time! And I hadn't been big-time," he laughs, "in a LONG time."
And even now, he is candid in acknowledging the questions that persist for him, questions underlined for him in making this film.
"A lot of things about myself newly mystified me," he says. "Forget that you did it, forget that you were there, forget that all this bumped into your life. Why YOU?"
He is still sorting out why him and what his life's work means.
"Each time we achieved something," he muses, "I woke up the next day and I said, 'We got it! We did it!' But we didn't get it: Here we go again."
Fittingly, his film ends not with a declaration, but with him posing a question, and a call to arms for fellow activists: "What do you do now?"
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