Luke Treadaway (Brian Sweeney/Roadside Attractions)

Tonight You’re Mine is a cheerfully rocking alternative to Hollywood’s sappy, romantic comedies. The setting at a real, raucous summer music festival adds a lively atmosphere to the usual conventions of opposites meeting cute. Director David Mackenzie has featured highly charged couples before—Young Adam (2003), Asylum (2005), and Perfect Sense earlier this year—but those steamy matches didn’t have the joie de vivre energized by the filmmakers’ being embedded at the T in the Park Festival in central Scotland. It is one of those sweaty summer weekends that Bonnaroo in Tennessee is modeled on, with multiple stages, a fairway with a Ferris wheel and arcades, a huge campground, and ecstatic crowds.

The bit silly plot gimmick is that from almost the minute they meet the couple can’t stay apart for the next intense 24 hours. In the back of a limo, the headlining duo the Make is debuting a new retro-pop love song for a web interview—Adam (Luke Treadaway (one of the twin rockers in 2005’s Brothers of the Head) accompanied by Tyko (Mathew Baynton). (Their song “You Instead” was the film’s title in the U.K.) In the festival’s equivalent of the performers’ green room, their commercial appeal is mocked by the four women in a riot grrrl punk band, the Dirty Pinks (which leads the guys to retort with rude vagina jokes). A Jamaican security guard interrupts their arguments to promote the festival theme of peace, love and (mis)understanding by handcuffing Adam with the Pinks’ mouthy lead singer, Morello (Natalia Tena), and then he disappears.

As these two defiant ones run all around the site searching for the key master, their bickering-into-romance storyline is integrated into the ebb and flow of this giant event: the side tents for up-and-coming bands; the VIP passes that separate the performers from the hoi polloi into nicer yurts; bathrooms and showers after the (inevitable) rain storm; a late-night drug-fueled, DJ-led electronica dance jam; the crowd-waving rhythmic sing-alongs to the headliners; and even the giant video screens for the (predictable but satisfying) climax. Actual performances at the 2010 festival add to the verisimilitude, including the Scottish band the Proclaimers—their catchy chorus to “I’m Gonna Be (500 Miles)” is enthusiastically chanted by the throng.

The secondary characters make good-natured fun of music and movie stereotypes, but aren’t too bland for comic relief. Adam has a supermodel girlfriend, Lake (Ruta Gedmintas), who is just out of rehab; Morello’s boyfriend Mark is a banker (played by the director’s brother Alastair Mackenzie), and the band manager Bobby (Gavin Mitchell) lets loose in drunken slapstick. But Treadaway and Tena are the magnetic roller coaster at the center. Casting actors who can also rock particularly pays off in the key scene that establishes the couple’s chemistry when Adam is dragged along into what is an important gig for her in the small “Futures” tent. He first annoys her on keyboards, but then they generate heat onstage with a segue into a catchy cover of “Tainted Love.” Tena came right from performing at the Glastonbury Festival with her band Molotov Jukebox to the film’s set, while Treadaway co-wrote his fictional band’s songs, including the title number, with Eugene Kelly of the Scottish band Vaselines, in the style of MGMT and the Killers, who have both headlined at the T in the Park Festival (named for its beer company sponsor).