Director John Carney’s continuing exploration of the magnetic attraction of music to bring together unlikely cinematic pairs has now canonically conjoined Paul Rudd and Nick Jonas. The dramedy Power Ballad (B) follows Rudd’s character, a wannabe arena rocker who has settled into fronting a wedding band in Ireland, home to his wife and daughter. One night he drunkenly bonds and musically riffs with the Jonas character, a boy-band member in search of solo stardom. Soon an unexpected global hit song is born, and it’s not totally clear the tune’s baby daddy. It’s nice to see Rudd sink his teeth into an authentic and scrappy character. Jonas is a good fit as well in his role, with confidence cloaking just a dash of desperation. Carney’s film takes a hot minute to gain steam but is worth the patient watch for the payoffs. Jack Reynor is particularly effective as a very direct American music mogul and manager critical to the copyright custody battle of a plot. The movie also hinges on the ear-worm original song titled “How to Write a Song Without You,” and fortunately it’s a banger. With lively performances, at least one hummable new tune joining a bunch of covers sung by the starring duo and a bit of sentiment and Irish charm, it’s an enjoyable entry into Carney’s cinematic songbook.