The Fiery Furnaces, Scala, London

The fact that The Fiery Furnaces took their name from both the Bible and Chitty Chitty Bang Bang gives a sense of the extremes they operate at. Hailing from Chicago but now firmly grounded in Brooklyn, Eleanor and Matthew Friedberger are a sibling double act, and their debut album, Gallowsbird's Bark, is a riot of restless invention.

Its songs veer giddily between innocence and experience, conjuring up images of a 1970s New York art-rock theme party in a fairground, or folk-blues in toytown, taking in roots Americana, chugging riffs, garish organ flurries, nursery-rhyme-speak, wonky piano, wah-wah guitar and Waits-ian discordance. The ones that aren't about bubonic plague and photocopier mischief in bad office jobs tend to be inspired by Eleanor's world travels.

Sonically, it's a heck of a trip. And that's before you get to the live set. Having bounded on stage like Rocky in a prize fight, and raced emphatically through "My Dog Was Lost and Now He's Found", Eleanor announces that they're going to play "several songs, really fast". And they do just that: with Eleanor and Matthew backed by a bass-player and a spectacularly excitable drummer, they barely pause for 40 minutes, cramming a dizzying whirl of energy, ideas and songs into an all-too-short set.

Much of the album is dramatically reworked, and, unlike what happens when, say, The Sleepy Jackson try that, the results are exhilarating. There is genuinely never a dull moment. Mood and rhythm changes are flung out full pelt, as the drummer flails and Matthew peppers fuzzy guitar runs with antique organ swirls.

There's something undeniably 1970s New York about the Velvets-style chug and psychedelic swell of, say, "Bow Wow", but as for the type of studied, Big Apple ennui of The Strokes - well, there's just no time for that.

That the show doesn't deteriorate into chaos is to Eleanor's considerable credit. She's a captivating frontwoman, with her jerky moves and androgynous - especially with her fringe and leather jacket - Patti Smith-meets-Joey Ramone look. While her sing-speak vocal volleys are eccentric, it gradually becomes clear that the clarity of her delivery is the focus for the sonic mayhem around her. The pace is so frantic that the melodies initially prove elusive, but they do take shape, particularly on the mesmerisingly strange child-song single, "Tropical Ice-Land".

I'd hoped they would play the more music-hallish romps from their album, but that's probably like complaining about the type of matches used to light a £1m fireworks display. As it stands, The Fiery Furnaces produce a kaleidoscope of sound, and when they strip things bare - as on a lovely encore of "Rub-Alcohol Blues", with its "My heartstrings broken to shreds/ Blues creeping over my body" - they deliver as direct a punch as that other blues-baked, (ostensibly) brother-sister duo.

More of that, and The Furnaces will be unstoppable. They're certainly challengingly singular, but it'll only take one hit for bigger audiences to be theirs for the taking.