The Lionheart Brothers prove that the live experience can be totally different from the studio. On their recent Dizzy Kiss album, the Norwegian sextet offered aural confections: perfectly crafted, vocal-laden psychedelic pop with a nod to the Beach Boys. Live, they are unexpectedly transformed into rock beasts. A mass of flailing hair, twin frontmen-guitarists Marcus Forsgren and Morten Øby display the up-and-down boogie movement beloved of Status Quo's Francis Rossi and Rick Parfitt. Every so often, Øby will throw himself to the floor for no apparent reason, while drummer Peter Rudolfsen hits his drums as if he were hammering a fencepost into the ground.

Forsgren is clearly on a mission to reclaim the bandana from Mark Knopfler and Axl Rose, and has so many effects pedals that they can only be reached by his enormous winklepicker shoes. It is not exactly what was promised, but they are rather fun.

If Dizzy Kiss is all gossamer and polish, this live show is about volume and repetition. Their steamhammer grooves recall cult 70s German band Neu! and British noise groups Loop and Spacemen 3. When the killer guitar hooks lock into the twanging bass countermelodies, they are hypnotic. However, an inferior performance of the album track 50 Souls and a Discobowl - with virtually inaudible vocals - makes you wonder if they are meant to sound like this, or whether the Brothers have been fiendishly transformed by a mischievous soundman with a fetish for krautrock and the Ramones.

Not that the crowd seem bothered, especially the two audience members who dance as if they are undergoing electrocution. "Thank you - especially those two. Whoo!" says Forsgren, and then makes the metal "devil horn" finger-sign above his head. Maybe they are rock monsters after all.

· At the Soundhaus, Northampton, Thursday. Box office: 01604 604020. Then touring.