Unseen footage of Rolling Stones at notorious festival found – Watch it here

The home movie is vividly shot on 8mm film but it is not known who filmed it

Twenty-six minutes of unseen footage of the vast and notoriously violent Altamont music festival held in northern California in 1969 have been unexpectedly uncovered.

The home-movie footage – which is vividly shot on 8mm film, but frustratingly silent – has been published by the US Library of Congress on its website.

It is not known who filmed it, as the footage had been left with a film development company and never collected. When the company, Palmer Films, went out of business in the mid-1990s, a cache of its films were acquired by archivist Rick Prelinger, whose large collection was in turn acquired by the Library of Congress who have been working to edit and publish the footage ever since.

The Rolling Stones' headline performance is filmed from the side of the stage, with closeup shots of a smiling, clapping Mick Jagger – as well as more tense and frenetic scenes, as burly Hells Angels flank the stage.

The motorcycle gang had been hired to provide security, but had attacked both performers and attenders during the day. During the Stones' set, one festival-goer, Meredith Hunter, attempted to get on stage along with a number of other fans. Separate film footage showed that Hunter was carrying a gun, and he was stabbed and killed by Hells Angel member Alan Passaro. Mike Mashon of the Library of Congress states that the footage "doesn't add anything to our understanding" of the killing.

Hunter's death, and the reportedly bleak mood of the event more generally, has become symbolic for the corruption of 1960s hippy idealism. The festival was separately chronicled by directors Albert and David Maysles and Charlotte Zwerin for the film Gimme Shelter.

As well as giving a sense of the huge scale, and some choice dance moves and fashion of the era, the lost footage is an opportunity to see performances in more detail that were edited out of the Stones-focused Gimme Shelter. It features an energetic and clearly funky performance by Carlos Santana and his band, and Crosby, Stills, Nash & Young are filmed in the golden light of sunset – they didn't appear in Gimme Shelter at all, as they told the directors they weren't happy with their performance.

Grace Slick is filmed charismatically fronting Jefferson Airplane, and the film-maker captures scuffles with Hells Angels on stage, including one audience member being pushed off and threatened; singer Marty Balin was infamously knocked unconscious by one of the bikers during the performance.

Mashon writes of a barechested and magnificently hirsute Gram Parsons: "It was especially great to see Gram Parsons fronting the Flying Burrito Brothers, since you only see the back of his head in Gimme Shelter. Even better, there are good shots of Mick Jagger and Keith Richards off-stage watching him perform."

Mashon told the Washington Post regarding the unknown film-maker: “If an owner emerges, certainly we’d be interested in hearing that. Somebody with proof. But as far as we know this film was abandoned.” – Guardian