Muhammad Ali fought George Foreman for the heavyweight championship of the world in Kinshasa, Zaire (now the Democratic Republic of the Congo), in the epic 1974 "rope-a-dope" battle, known as the Rumble in the Jungle, that was documented in Leon Gast's film When We Were Kings.

But Gast's masterful 1996 film told only half the story.

The Ali-Foreman face-off was twinned with a second spectacle, a three-day music festival called Zaire '74. James Brown, B.B. King, Bill Withers, the Spinners, and Philadelphia's own Sister Sledge made the trip from the United States, Celia Cruz and the Fania All-Stars brought salsa from Cuba, and many of Africa's biggest stars also performed, including South Africa's Miriam Makeba and Zairean giants Franco and Tabu Ley Rochereau.

For legal and financial reasons, the footage - much of it shot by ace documentarian Albert Mayles - has not been seen for 35 years. (Alas, a deal for a sound-track release still hasn't been struck.)

But the passage of time - and the passing out of fashion of scoop-chested bell-bottomed rhinestone-studded unitards, such as the one Brown wears with the letters GFOS stitched at the belt - only adds to the magical quality of director Jeffrey Levy-Hinte's explosively exciting film.

What does Soul Power have going for it, besides Don King's hair, Muhammad Ali's charisma, and the best jamming-on-an-airplane-to-Africa sequence ever filmed? Well, for one thing, it packs the emotional and historical power of a heady "family gathering" celebration of African and, to use the term then in fashion, Afro-American pride.

"Say It Loud - I'm Black and I'm Proud," Brown's climactic closer, resonates equally with the American performers and the African audiences.

"It's so peaceful over here: The savages are in America," opines Ali, who is playful, magnetic, and politically agitated in his interview segments. In one he corrects a reporter who suggests that all men are brothers, since in Ali's view brothers don't lynch one another.

Soul Power doesn't have a political agenda so much as a musical one. It's about African and American rhythmic communication, expressed succinctly in percussionist Ray Barreto jamming with Zairean musicians on the streets of Kinshasa, or Sister Sledge teaching African dancers how to do the bump backstage.

The festival, organized by King, New York record producer Stewart Levine, and South African trumpeter Hugh Masekela, took place six weeks before the fight, which was delayed after Foreman injured his eye while training. And the performers are caught at the height, or nearly so, of their powers.

Unlike so many music documentarians, Levy-Hinte has the good sense to let each scintillating performance go from beginning to end. Everybody except the sweaty, mustachioed, ultra-dynamic Godfather of Soul, who muscles his crack band through "Soul Power," "The Big Payback," and "Cold Sweat," among others, gets one song.

All make the most of the moment. Withers' solo acoustic lament "Hope She'll Be Happier" is a stunning crowd-silencer. And the pipe-smoking B.B. King, delighted to "see some beautiful ladies" as the the plane touches down on African soil, is at his swaggering, note-bending best on "The Thrill Is Gone."

Three and a half decades down the line, the Zaire '74 promoters deserve major props for booking acts whose music thrives on intercontinental rhythmic conversation, whether it's the Afro-Cuban stylings of the outrageously outfitted Cruz and the Fania All-Stars or the Western-influenced pearly guitar sound of Tabu Ley's soukous amalgam.

Soul Power doesn't employ any after-the-fact pontificators, or interviews about the significance of the event. Levy-Hinte, who has said there's enough unused footage for a second concert film, understands that there's no need to over-contextualize or dilute the splendor of what transpires on the screen. He's smart enough to let the music do the talking.EndText

Contact music critic Dan DeLuca at 215-854-5628 or ddeluca@phillynews.com.