All bands end up hating each other, but it’s practically where Dinosaur Jr started from. “I don’t know where people get this idea that playing music is supposed to be fun,” says J Mascis in Philipp Reichenheim’s new documentary, Freakscene: The Story of Dinosaur Jr. “I guess we never had that.”

A younger Mascis played hardcore drums to 33rpm records spinning at an extra fast 45. “I was just sick of all that hippy shit,” he says. Backing his belief that expecting fun from making music “hinders a lot of people”, he ditched the instrument he truly loved, picked up a guitar that he’d soon master and formed Dinosaur Jr with drummer Murph – a stoner hippy, of course, who was “attracted to J’s anti-everything attitude.” “I always thought he hated me, so I don’t know why he wanted me in his band,” says bassist and final Dinosaur member Lou Barlow.

The obvious question is why do it then? Although don’t expect that to be answered by Freakscene, which shares a lot (rather enjoyably) in common with the band it documents, including a vagueness that’s forever been connected to Mascis in particular. He talks on camera in his slooow Massachusetts drawl, seemingly unmoved by even the band’s most turbulent times, not pulling his punches but not explaining them away either. Barlow and Murph follow suit, the three of them seemingly numb to how they felt (and feel) about one another and what’s gone on between them since 1984. They’ve asked themselves another question: why bother figuring out why we do this now?

Director Reichenheim’s new interviews with the band don’t probe for good reason: for one, he’s Mascis’ brother-in-law, and presumably knows very well the blank stare he’d get in return for asking for elaboration; for another, there’s a lot to get through, and so the film continues at pace, albeit after the overly long opening credits that play out ‘Freakscene’ in its entirety yet forgets to include the credits themselves. It’s a minor quirk that also befits band and film, made up, as it is, of vintage VHS live footage, cut-n-paste show posters and talking heads for a zero-dollar budget – a valuable, nostalgic glance back into a DIY aesthetic that no longer feels possible.

The cast of those talking heads – seemingly recorded over the last 10 years or so – is impressive because it features everyone you’re expecting it to and someone you’re not. Joining My Bloody Valentine’s Kevin Shields for some kind (and true) words on Dinosaur Jr are Kim Gordon, Bob Mould, Henry Rollins and Thurston Moore. Frank Black makes a brief appearance too, to try to explain what makes them such an important band. He fails, of course, but it’s fun watching him talk complete bollocks while he tries. At one point he’s just making noises and jamming his fingers together.

“I didn’t hate J until the later years,” says Barlow. Mascis marks the beginning of the end as far back as before the release of You’re Living All Over Me in 1987. Maybe it’s comforting to know that even rockstars stay in jobs they hate for too long.

Freakscene: The Story of Dinosaur Jr opens in selected UK cinemas Oct 1