Power Ballad: Paul Rudd and Nick Jonas lead this warm-hearted comedy about pop stardom and fading ambition

Power ballads have a formula – a slow, soft piano intro say, with a heartfelt lyric that gradually builds up to an epic chorus and sweeping orchestration, whether it’s Cher on a battleship, Meatloaf on a motorbike or four presentable young men on stools. And Power Ballad’s writer-director John Carney has something of a formula, established in films like Once (2007), Begin Again (2013) and Sing Street (2016), in which a plucky outsider – often a musician, often in Ireland – finds some kind of happy ending or vindication, musically, romantically or both. Power Ballad doesn’t stray far from what is a satisfying formula, but it does play subtly with expectations.

The story is sparked when Rick (Paul Rudd), a failed American rock musician who now works as a wedding singer in Dublin, reluctantly agrees to share vocals at a reception with Danny Wilson (Nick Jonas), an old friend of the bride and groom – who also happens to be a former boyband member turned solo act. Danny’s singing impresses Rick, and the two end up bonding in an after-hours jam session during which, fuelled by weed and Irish whiskey, they swap notes on each other’s songs. Carney lets this scene run on towards Richard Linklater all-nighter proportions, and Power Ballad seems to be setting up a bromantic plot in which the two, after an inevitable conflict, will be happily reconciled, and probably collaborate. “What a great kid,” Rick repeats to himself as he admires a rare guitar Danny has given him on the drive home with the band. And when Danny returns to LA and records one of Rick’s songs, ‘How Could I Write a Song (Without You)’, as his own, we have the conflict: Rick’s song becomes a mega-hit for Danny, relaunching his career, but sending Rick into a spiral, as he tries to convince bandmates and family the song is actually his, despite being unable to find any demo or other recording of it as proof.

At this point Carney’s film is as much about power balances as power ballads, with Rick running up against the corporate wall represented by Jack Reynor (star of Lenny Abrahamson’s portrait of gilded Irish youth What Richard Did, 2013): he plays an all-American entertainment industry shark on the pattern of Scooter Braun (former manager of Taylor Swift and Justin Bieber). Legally, Rick’s lawyer tells him, he’s out of options. “And illegally?” asks his guitarist and sidekick Sandy (Peter McDonald).

While Danny is set up as the villain, Carney refuses to simply paint him as the bad guy. His plagiarism comes as his career is on the ropes, but it’s his girlfriend’s reaction as he plays through Rick’s song at home that leads Danny, caught out by the moment, to lie that the song is his. When Rick eventually tracks him down and confronts him in LA, Danny points out that while Rick had the song, he couldn’t have made it a hit – it took Danny’s vocals and delivery to do that.

Carney’s script at times feels undercooked by Hollywood comedy standards; then again, it’s restfully free of the writers’-room need for wall-to-wall cracks or competitive ad-libbing. A slight suspension of disbelief is required to imagine the songs (also written by Carney) as streaming smashes. But what elevates Power Ballad is the casting: Jonas brings an easy-going humility to a character who, from certain angles, could be a parody of his own career as a former boyband singer. Rudd lends a level of charisma and a paradoxically grizzled youthfulness that make Rick’s ambitions and idealism seem plausible. In an inversion of Adam Sandler’s character in The Wedding Singer (1998), Rick has become a wedding singer because he’s married, and has parked his fragile musical ambitions for the reliability of a paycheck. At one point, he plays a demo of one of his songs for his unimpressed daughter Aja (the name presumably a nod to arch-cynics Steely Dan). Teenage girls don’t want to hear love songs any more, she tells him; what do they want? “Revenge,” she says, channelling Olivia Rodrigo rather than Adele. Aja is, in the end, the one character who always believes Rick wrote Danny’s hit, and is the one who helps the truth come to light. The payoff at the end of Power Ballad is not revenge so much as a pay-out.

► Power Ballad is in UK cinemas 29 May.