“I’m not playing the ukelele,” says Clara, a moody thereminist portrayed by Maggie Gyllenhaal, toward the end of Lenny Abrahamson’s Frank, a sentiment some viewers may interpret as a critique of the appetites of the modern indie hypebeast. And, sure, that’s definitely one thing on the mind of Abrahamson and his scripters, Jon Ronson and Peter Straughan: This is, after all, a movie involving an unknown band, minor Twitter and YouTube celebrity, and a potentially game-changing showcase at South by Southwest.

A few things about that band, though: They’re called the Soronprfbs (try saying it out loud); they play demented psych-rock with a touch of novelty music and new wave; and they’re led by Frank (Michael Fassbender), a mysterious singer with Jim Morrison’s croon and a giant papier-mâché head mask he never takes off. When we meet them, their keyboardist is being hauled off to a psych ward after trying to drown himself. Later, they hole up on a remote Irish island, recording the sounds of door hinges, inventing a new musical notation system, and attempting to find, according to Frank, their “furthest corners.” The buzz industry that floods this editor’s inbox each day with new tracks and late-night TV appearances wouldn’t touch these guys.

On one level, Frank is the story of an outsider band tempted and undone by the calling of fame—there are debates over authenticity and accessibility, and tropes like a drummer (Carla Azar) who barely talks—but it’s also stranger and funnier and more humane than that kind of film usually manages to be, and it’s ultimately much more tragic, too. Its questions are certainly more interesting: Where do you look to make something meaningful and beautiful? (Should you, as one character puts it, “stretch your corners” for the public’s embrace?) How do you nurture someone’s creativity? And when that creativity is tangled up in what must be mental illness, do you have a right to exploit it?

Standing in for the audience, as well as for some horrible and banal human instincts, is Jon (Domhnall Gleeson), a young man who concocts terrible lyrics about his bleak English suburb (“lady in the red coat, what you doing with that bag?”) that he can never translate into a proper pop song. He fires off vaguely aspirational, possibly unironic tweets like “cheese and ham panini #livingthedream.” He dreams of stardom. Enter the Soronprfbs, whose sadsack manager (Scoot McNairy) enlists Jon to play keyboards at a show that goes haywire and then invites him to record with them. In turn, Jon posts footage of the Soronprfbs’ rehearsals online, and the clicks multiply.

“What goes on inside the head inside that head?” Jon wonders about Frank, but Fassbender’s masked performance is remarkably expressive. In one gag, he dictates his facial expressions (“flattered grin, followed by a bashful half-smile”), though he hardly needs to: A cock of his head, a gesture of his hands, a stare into space and Frank’s still face moves from creepy to inspiring to empathy-inducing. Frank, we learn, spent time in an asylum, which leads Jon, the lesser talent, to muse, “Miserable childhood, mental illness—where do I find that kind of inspiration?” Anyone familiar with Syd Barrett or Daniel Johnston wouldn’t ask that question so eagerly.

But along the way to Frank’s hyperactive and then crushing denouement, the Soronprfbs’ farcical mystery tour—and its eerie, delightful original songs, which feel like the 13th Floor Elevators as interpreted by the Residents—is a blast, at least as long as you’re willing to go to those furthest corners.

Maybe you won’t be. As part of Frank’s marketing, the Soronprfbs performed on The Colbert Report and launched a fake Facebook page. “They totally SUCK!” wrote the only commenter so far. “There’s so many worthy bands out there that are great and somehow this train wreck of no talent made it to my TV? I think stuffing a sharpened pencil in both my ears would sound better.” That’s exactly the kind of grief a delicate, eccentric talent like Frank should never have to endure.

Frank opens Aug. 22 at E Street Cinema.