Stage right, a 50s biker chick thunks a contrabass balalaika etched with the face of a winking Cheshire cat – a gigantic triangular plough of an instrument that looks like someone's put three strings on a stingray. Stage left, a Parisian flapper plays xylophone, harmonica and accordion all at once. At the back, a glamorous marathon runner juggles drum duties with bashing trashcans and carillon bells and, up front, a woman resembling Britney Spears's mum strums a furious Charleston on the banjo. This is Katzenjammer from Oslo, four multi-instrumentalist women with a cartoon aesthetic, a burlesque bravado and a name that's German for "hangover", though the only headache they induce is from their head-spinning cavort through the retro stylebook.

Just as their setup is a musicologists' wet dream, this instrument-swapping carnival at first seems a fantasy band designed, lucratively, to coat a mainstream-pop gloss on to Mumford & Sons's energised trad-folk revival. TV talent show stars in Norway, they're rooted in Balkan folk, bluegrass, country, Weimar cabaret and rock'n'roll. But they also display a commercialised edge redolent of the more berserk eastern bloc Eurovision entries. The recent single I Will Dance (When I Walk Away) from their second album, A Kiss Before You Go, imagines a Cossack Shakira, while To the Sea could be Marina and the Diamonds' take on a Viking shanty.

As their set progresses though, they abandon Mumford's coattails for something more adventurous: moving choral balladry (Lady Marlene); 20s barbershop hula (Cherry Pie); brilliant, cranky art-pop about fetishes (Cocktails and Ruby Slippers); a Germanic oompah version of Genesis's Land of Confusion; and a number called Le Pop that's practically J-pop. In lesser hands, the guitar would be the star, but Katzenjammer will soon be just as oversized.