If the joke is that you're a failed band, two losers with only one fan, what do you do when you become one of the hippest acts in international comedy? That's the paradox facing Flight of the Conchords, "New Zealand's fourth most popular folk parody act", as they used to call themselves before their hit sitcom and now tour of Britain's enormo-domes. The contradiction is unresolved: Bret McKenzie and Jemaine Clement seem unsure whether to stay in gormless character or savour their success. But if the Conchords concept is looking shaky, the songs are solid as ever: masterpieces of bathos that unite earnest musicianship with pedantic and gloriously banal sentiment.
I say songs, but the gag is that Clement and McKenzie's lyrics seldom attain that status. Songs require heightened language, but the pair trade in an earthbound idiom, and their funniest numbers are marooned between music and hair-splitting chat. When they want to look like macho rappers, they bellow phrases such as: "Be more constructive with your feedback!" Two ex-lovers recalling their night together get bogged down in a critique of the film Weekend at Bernie's II, and a medieval madrigal about wooing falters at Jemaine's difficulties in renting a horse.
More than in their previous shows, Clement is the star here. His personality inflates to arena size, whereas McKenzie's stays put. Their music – finest when plucked and twanged on acoustic instruments – and their Kiwi deadpan are better suited to smaller auditoriums: tonight's event is low-key by arena standards. But concessions are made to showmanship: the pair shimmer in sequinned bodysuits on Bowie in Space, and their trapped-wind R&B caterwauling would be hilarious whatever the venue. Likewise their imperishable banter. "If you're wondering," Clement tells us, "this is one of the talking parts of the show. It's just normal talking, except it's more professional."
The Conchords' most delightful dotty material derives from a nit-picking refusal to let anything speak for itself. The lyrics puncture their own illusion. "Oh Jemaine, you're amazing at making love," sings Jemaine on Business Time. Then he answers himself: "Thank you, me-putting-on-a-lady's-voice." They're hyper-sensitive to gradations of reality and illusion, which is why the uncertainty about their own identity (they respond to a heckle about their manager Murray by referring to him as a fictional character) is conspicuous tonight. But by the end, there's no room for confusion. As they bump, grind and thoroughly enjoy themselves among their adoring crowd ("Ladies from the easties and from the westies / Trying to molest these beautiful testes"), no one will mistake them for failures.
