They Might be Giants, Shepherd's Bush Empire, London

Giants no more play prog-rock with attention-deficit disorder

Ironic, geeky, inauthentic, whacky – the accusations levelled at They Might Be Giants, one of the definitive early American "College Rock'' bands, sum up why they've slipped so far from sight these past few years.

Their influences suggest a more complex picture. Named after an eccentric, idea-packed George C Scott film, the band appropriately came to fame slapping down a song a day on their answerphone for fans to listen to, while musical influences include the artily cerebral Residents and the worryingly innocent Jonathan Richman. They Might Be Giants fell neatly between those poles on speedy, witty early 90s hit singles such as "Bird House of Your Soul''. They never expected such success to last, and have ticked over, writing TV themes, ever since. Now, though, on their upcoming album – the first in five years – they sound tinny, inessential, like men who really should be told their time is up.

But it won't be this crowd that breaks the news. Which woodwork they crawled out of can only be guessed, but the Might Be Giants fans here were unexpectedly numerous and rowdily vocal. When the confetti fluttered down on them soon after the guitarist John Flansburgh and keyboardist John Linnell took to the stage, there was an air of celebration and revival. It was dissipated only by the music that followed, which for a long time showed why most ears are now closed to it.

They Might Be Giants have a magpie's attitude to pop, inserting parts of show tunes, drum solos, medleys, skipped CD sounds and ironically conducted guitar breaks, with lyrical concerns ranging from dead presidents to shoehorns. But 70s-style instrumentals remain dull no matter how satirically they are intended or how cleverly they are played. It's like prog-rock, with attention-deficit disorder.

It's only near the end of this two-hour set that the nervy jokiness settles down, and the crowd's affection brings out something more substantial. It starts with bright, unaffected garage rock, before a melodic, thoughtfully sung obscurity from 1996, "Pet Name''. "Bird House In Your Soul'' – introduced as "our big song, once'' – is a forceful reminder as to what they can do; its massed, thrashed guitar chords and bouncing chorus played with full passion.

When they then emotionally blackmailed the audience into buying their new single, "Boss Of Me'' (Malcolm in the Middle's theme tune), it was both the night's funniest joke and a request that's hard to resist, especially as it shares their old hits unabashed, quirky bounce. They don't know their own strength but they deserve to carry on.