Writer-director John Carney has become something of a cottage industry, making charming Dublin-set films about everyday people who love to make music whether it brings them fame or not. Movies like Once and Sing Street are designed to make you believe in the power of DIY music magic. They may be gentle pictures, but they remind you that just strumming a guitar can have transformative powers. They’re feel-good movies brushed with just the right amount of wistfulness.

On the surface, Power Ballad—which Carney co-wrote with Peter McDonald, who also appears in the film—promises more of the same. Paul Rudd stars as Rick, a middle-aged Kansas-city-born rocker who’s been living in Dublin for 15 years: While on tour with his old band, he met and fell for an Irish girl and never looked back. That rock’n’roll girlfriend Rachel (Marcella Plunkett) is now his wife, and the couple have a smart, likable teenage daughter, Aja (Beth Fallon), surely named after the Steely Dan album, though no one feels the need to state as much.

Rick’s life has settled into a cozy track. He’s the lead singer of a successful-enough wedding band called the Bride & Groove, and you can see why people want to hire these guys for their nuptial bashes. These guys know their stuff, and they wheel through cover after cover with professional aplomb. Kool & the Gang’s “Celebration,” Thin Lizzy’s “The Boys Are Back in Town”: they can do it all, probably in their sleep, though they take care to make it look like fun. Rick is an easygoing, charismatic entertainer, the kind of frontman whose ready smile is the stuff of innocent flirtation. Every bridesmaid is safe with this guy—but a girl can still dream, right? Rick’s bandmates, all around the same age, vary from affable to irascible; the sweetest of them is McDonald’s Sandy, who lives with his mum and seems to look up to Rick as a guy who’s surely got it together.

But Rick hasn’t fully given up on his rock’n’roll dreams. He loves his family, but still he can’t help yearning for something more. When he and the guys play a wedding at a tony estate, they’re joined onstage for one song by a superfamous wedding guest: Danny, played by Nick Jonas, is, just like Jonas himself, a veteran of an explosively popular boy band. But his solo career has floundered. He longs to get back to basics but doesn’t know how. Though Rick is at first miffed at sharing the spotlight with a scene-stealing superstar, the two end up hitting it off. After the party, they stay up late into the night, drinking and sharing songwriting tips. Danny gratefully accepts Rick’s advice on a melody that needs help. Rick plays Danny a song he’s been working on for years but can’t quite get right. The two part cordially—Rick expects nothing more. Which is why he’s shocked just a few months later when Danny, having returned home to Los Angeles, releases a song that’s an instant smash hit—the very one Rick had shared with him.

The rest of Power Ballad focuses on how Rick tries to get his song back. There’s lots of humiliation and frustration involved, as well as an incident that endangers his family. It should all add up to the expected Carney magic—and yet somehow, it doesn’t. The performers aren’t to blame here; it’s the story that lets them down. As Danny, Jonas—with his butter-smooth stage moves and creamy crooning—is almost alarmingly appealing. You can see how he could instantly captivate not just adolescent girls, but their moms as well. (At one point, Danny reveals one of the keys to becoming a successful boy band: you’ve got to win over both the kids and the parents with your wholesomeness, because it’s the parents who hold the purse strings.) And Rudd, as the happy mid-lifer who can’t help wanting a little more, is appealing in that characteristically boyish, Rudd-like way, though there’s also something deeply wistful about him. Rick knows he should be completely happy with his cool, beautiful wife and nobody’s-fool daughter. (At one point, she informs her dad that old-school love songs no longer cut it with young women because they’re uninterested in falling in love. When he asks what they are interested in, she says, with the scalpel directness of a teenage girl, “Revenge.”)

If middle-aged disillusionment can touch Paul Rudd, what defense do the rest of us have against it? But even more than that, Rick has been betrayed in a deeply personal way, which may be why it’s so painful to see him crushed. Power Ballad should be breezy and fun, with that twist of mournfulness that Carney is always so adept at pulling off. And yet—when a person steals your song, they may as well be stealing part of your soul. And to see that happening to a character played by an openhearted actor like Rudd is almost too much.

The movie sets it all right in the end. Yet Power Ballad left me feeling not rejuvenated but mildly depressed. We live in an age when people who stand to make a ton of money off AI are reassuring us that it’s simply a tool to help us be more efficient and creative; the mysterious roots of human inventiveness are now a thing that can be commodified. There’s no AI in Power Ballad—both the creativity and the thievery it depicts are the old-fashioned, purely human kind. Even so, the movie springs from a horrifying premise: that an idea you’ve protected and nurtured for years can be stolen away from you in an instant by someone more powerful than you are. Wittingly or otherwise, Power Ballad is all about the preciousness and fragility of human creativity. And maybe, right now, its belief that everything can be put to rights with a happy ending is a fantasy too sad to bear.