Black Power Mixtape 1967-1975

This is a strangely kaleidoscopic approach to documentary. A selection of recently unearthed footage and interviews which shows the Black Power movement in the USA through the eyes of idealistic Swedish film-makers, now re-edited and framed with the voices and music of both modern and veteran black radical cultural figures, it provides a disorienting, shifting set of superimposed viewpoints of a period in which in any case change seemed to be the only certainty.

The footage itself is gripping and often truly eye-opening, particularly when it's at its most ordinary. The stories of dramatic injustice, and the recordings of Black Panthers and Nation of Islam representatives spitting fire and vengeance on podiums and on the street, though they may still have the power to rouse and rile, are familiar from endless pop-historical TV series, their power perhaps dimmed by repetition. But when we see sympathetically shot footage of ordinary lives, or the iconic radicals of the time caught off guard, the era is really brought to life.

Stokely Carmichael chuckles and lights a cigarette at a press conference, or is seen crouching in his mother's living room as she is interviewed herself. Martin Luther King looks very small and uneasy meeting the King of Sweden. Angela Davis is interviewed in her prison cell, where we can see her defiance tainted with hints of desperation, and her furious intellect working overtime keeping her guard up to avoid being wrong-footed by the gentle, deadpan questioning of her Swedish interlocutors (their style, perhaps, a very early unconscious forerunner of the Nick Broomfield/Louis Theroux ingénu school).

The accumulation of tiny details like this begins to build a very human picture of a time of revolution and disillusion. A tangled tapestry is woven of crushing grievance, heartfelt hope and starry-eyed naivety, historical inevitability and stoned self-aggrandisement, fierce pride and grim fatalism, with a background of Nixon, Vietnam, prison massacres and a European climate that would create the likes of the Red Army Faction... It's heady stuff – and made more real by that sense of the ordinariness that made up most of life around the drama.

And then on top of all this, we have the voices of 21^st-century activist musicians like Erykah Badu and Talib Kweli, and those of radical figures from the era in question including the stentorian tones of Abiodun Oyewole of the Last Poets, musing on how the events documented reverberate and how much has changed today. Given the tension and violence depicted, its pace is oddly relaxed, and one can find oneself slowly, gradually drawn into the confusion that still reigns over the racial politics of the USA. And it's precisely because of that confusion that the multi-voiced, multilayered approach works, with neither slobbering "radical chic" nor earnest sermonising allowed to dominate and despite – or even because of – its lack of answers and clarity, this remains a film that greatly rewards patient viewing.

• Black Power Mixtape 1967-1975 is in selected cinemas from today