The scruffy-looking fellow hunched over a table in a roadside restaurant deep among the redwood forests south of San Francisco does not look like a rock superstar. He has a craggy face, like a weather-beaten farmer, unkempt hair swept back behind his ears, and grey mutton chops; he is wearing combat trousers, trainers and a baggy T-shirt over a modest paunch. Only the big wraparound shades and the legend on his T-shirt — a US patent-office application for the Gibson Flying V guitar — hint that this is one of the most influential musicians of the past 40 years, a figure with a body of work matched only by Bob Dylan.

Neil Young has never much cared for appearances; never needed to, and definitely doesn’t now, at the age of 62. He probably looked a lot like this when he met his second wife, Pegi, here, in this same restaurant, more than 30 years ago. She was a waitress, he was a rock star, but she might be forgiven if she had taken him for a passing lumberjack. When he pulls on a huge plaid work shirt at the end of the interview, he looks as if he is about to go and fell some of the giant sequoias outside. Instead, he drives the short distance home in a cream-coloured vintage Mercedes running on biodiesel.

If Young had his way, we would all be driving on green fuel; indeed, he is developing a revolutionary motor vehicle that he hopes, one day soon, will “eliminate roadside refuelling”. First, though, he must talk about another project. CSNY: Déjà Vu is the latest film from the director Bernard Shakey. Not to be confused with any of Young’s other aliases: Joe Yankee, Joe Canuck, Phil Perspective, Clyde Coil, Dirigible Dan, Dr Shakes, Shakey Deal or plain old Shakey.

The film is a documentary about Crosby, Stills, Nash and Young’s Freedom of Speech tour, staged during the US midterm elections in 2006. But it is a far cry from Michael Moore-style agitprop. Young/Shakey has gone out of his way to present an impeccably balanced picture of America’s reaction to a tour whose repertoire consisted entirely of antiwar songs, from Buffalo Springfield oldies such as For What It’s Worth and CSNY’s era-defining Ohio to selections from Young’s 2006 album, Living with War. To this effect, their trip is narrated by an award-winning television journalist, Mike Cerre, who has covered both Vietnam and Iraq, where he was an “embedded” reporter.

The film begins with President Bush solemnly intoning “This country is at war”, followed by a right-wing radio presenter reading out the news that a “major terrorist plot” to blow up planes between Britain and America has been uncovered on the day that CSNY come to town to perform. . . “but Neil Young says it’s no big deal”. At other points, voiceovers of enthusiastic reviews of the shows are counterbalanced with scornful appraisals of the “ageing hippies’ ” attempts to rouse America into antiwar protest.

In the most memorable scene, hundreds of audience members walk out of a show in Atlanta in protest at the quartet encouraging them to sing along to Young’s song Let’s Impeach the President. It is compelling footage: as the lyrics are displayed on a giant screen, a chorus of boos swells, competing with the more fervent fans’ mass sing-along, and angry punters start to leave. Seemingly oblivious to the almost comical irony of leaving a Freedom of Speech concert in protest at the singers expressing their own freedom to speak out, they air their fury on camera as they leave. “Neil Young can stick it up his ass,” fumes a female fan; “Sonofabitch — I’d like to knock his teeth out,” a red-faced man declares. Young seems unconcerned. “Well, they were speakin’ out too,” he chuckles behind his shades. “They were just saying ‘F*** you, I don’t wanna have anything to do with this guy crossing my line.’ ”

For Young, who was one of the first musicians to respond to 9/11, with his 2001single Let’s Roll (titled after the supposed words of the passengers aboard flight United 93 as they attempted to overpower the hijackers), it was crucial that his film presented both sides of the story, rather than merely trying to preach to the converted. “It’s important to have the other side,” he says. “Plus, those people were part of the story, so why leave them out? We decided to have an embedded correspondent documenting the tour like he was documenting a war.”

Young insists he had no intention of trying to convert his audience to his views, which have turned almost full circle over the course of his career: following his initial anti-Nixon stance in the 1960s and 1970s, he expressed (qualified) support for Reagan during the 1980s, then became an outspoken opponent of Bush. Nevertheless, the timing of its release is no accident. “We thought the prime time to put this movie out would be before the general election,” he admits.

The film will be given worldwide cinema release, but Young has no illusions about its box-office appeal. “I don’t expect it to last long,” he admits. “I mean, let’s be realistic: it’s a film about war and a bunch of old hippies, so that’s the way the public will view it. We spent a lot of time on it, and it means a lot to us, but in the overall scope of things . . . it has a moment, and this moment is coming up, and after that it’ll be a DVD, then it’ll be gone. It’ll be a piece of history.”

The “moment” he is talking about is the American presidential election in November. Young may claim that he is not using the film to campaign, but he planned the Freedom of Speech tour to take place during the midterms and is deliberately releasing the resulting film as the campaign between Barack Obama and John McCain gets under way. Not that he has a vote: despite living in America for 40 years, he remains a Canadian citizen. “I’m Canadians for Obama,” he declares with a chuckle. “There’s nothing I can do to change being Canadian. I could get a piece of paper saying I’m American, and get a vote, but it wouldn’t change who I am. As far as voting goes, I think I’m voting with my mouth and with my art and with what I’m doing.”

He admits there have been times when he has considered leaving America, but insists he will stay — his Broken Arrow ranch has been home for the past four decades. “I have an American family,” he says. “My family loves it here. I love it too; it’s a great place. Just because things are happening that are not right, it’s not a reason to leave. I’d rather try to do everything I can to make it right.” He continues, with a certain degree of deadpan irony: “I came down here because this is the land of opportunity and I feel good. When they elect a president here, they call him the leader of the free world. So what the hell? Canada is one of the freest countries in the world, so I feel great — I got a leader down here, too.”

Does he really think America is a land of freedom in the post 9/11 landscape? “No, it hasn’t been free. Under Bush, it definitely took a huge dump, this recent seven years, but hopefully we’ll get the civil rights back.” He believes today’s generation of young Americans does not have the same spirit of rebellion that he witnessed in the 1960s because, unlike their parents, they are not threatened with military conscription.

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