Watching James Brown post-performance at the Zaire ’74 music festival as he buzzes with adrenaline is an intimate moment. The Godfather of Soul is perched, elated, on the chair in his dressing room. He looks straight into the camera and says: ‘Damn right I’m somebody.’

That he is, along with the rest of the stellar line-up at this festival that’s now the subject of a film called Soul Power. It tells the story of Zaire ’74; the brainchild of producer Stewart Levine and musician Hugh Masekela, who wanted to put on a show to coincide with the Rumble in the Jungle fight between Muhammad Ali and George Foreman. The dates didn’t tally in the end, but the festival happened against all the odds.

The footage has been locked away for the past 35 years but it’s still as fresh as the time it was shot. The featured artists include BB King, Bill Withers, Miriam Makeba and Celia Cruz, and one of the best moments is when they jam on the plane over to Zaire – Cruz is particularly lively and they all crescendo into a frenzy of singing, laughing and clapping. When the big night eventually takes place, the performances are awe-inspiring. Look out for Withers’s spine-tingling rendition of ‘Hope she’ll be happier’.

Not only is the music top quality, but the street shots are also a fascinating insight into 70s Kinshasa. Everyone’s dressed sharp and superfly in big collars, plaid blazers, striped shirts and tight trousers.

The film’s slated to debut at Glastonbury this year, as BB King might very well be a surprise guest at the festival. A UK-wide release follows. It’s a story that deserves to be shouted about.