The Magnetic Fields | Queen Elizabeth Hall, London

Stage left, a young lady sits primly at a grand piano. Stage right, two bookish-looking chaps sit on low chairs, cradling guitar and solid-bodied cello. They all listen politely as another young chap, perched on a bar stool centre-stage, takes up a tiny wooden ukulele of the kind with which George Formby once entertained a generation, and sings a song called "A Pretty Girl Is Like...".

Stage left, a young lady sits primly at a grand piano. Stage right, two bookish-looking chaps sit on low chairs, cradling guitar and solid-bodied cello. They all listen politely as another young chap, perched on a bar stool centre-stage, takes up a tiny wooden ukulele of the kind with which George Formby once entertained a generation, and sings a song called "A Pretty Girl Is Like...".

Clearly, rock'n'roll doesn't get much raunchier than this. This is The Magnetic Fields, the American alt.pop group who earlier this year released the triple-album 69 Love Songs, an extraordinary work which revealed the group's songwriter Stephen Merritt - the chap with the ukulele - to be the Noel Coward of his generation. Possessed of a droll sense of humour, a frame of lyrical reference that encompasses Busby Berkeley and linguist Ferdinand De Saussure, and an awesome facility with musical modes - album tracks range from Scots folk pastiche "Wi' Nae Wee Bairn Ye'll Me Beget" to the self-explanatory "Punk Love" - Merritt is obviously a talent to be reckoned with.

And a hugely prolific one at that: besides The Magnetic Fields, he fronts at least another three bands, while 69 Love Songs was originally intended to be 100 songs long, before being trimmed, with an almost audibly raised eyebrow, to the barely more manageable 69. But for all the quartet's preppy appearance and static stage manner, there's an undertow of dark humour which cuts as deeply as anything in the world of satanic rock music.

Take the opening ukulele number: rather than a melody, the things with which a pretty girl is compared, turn out to be a minstrel show and a violent crime, while the song concludes with the non-PC sentiment that "A melody is like a pretty girl/Who cares if it's the dumbest in the world/It's all about the way that it unfurls". Okay, so it may not be the real Slim Shady, but sometimes the slim stiletto of wit slips more readily into those places where the bludgeon of bluster can't reach.

Apart from a few numbers sung by pianist, Claudia Gonson, it's Merritt's lugubrious baritone croon that carries his songs, and which - abetted by the deep burr of Sam Davol's cello - determines the band's key range. With John Woo (not the thrills'n'spills film director, one presumes) adding a delicate tracery of fingerstyle picking, slide guitar and occasional plunking banjo, there's a rarefied air of palm-court refinement to the proceedings, as if Scott Walker were being backed by The Penguin Café Orchestra.

It's to their credit that they manage to wring quite as much variety as they do from such restricted instrumentation, illuminating Merritt's songs with a succession of fairy-light embellishments - pizzicato cello, high-register guitar twinklings, tinkly-bonk keyboard percussion, a tapped wine-glass or two - though there are moments when one yearns for the thunder of drums or a well-placed power-chord or two.

Or a Pete Townshend mid-air splits: the closest they get to stagecraft is when Merritt leaves his stool to take another slurp of wine or stroll about the rear of the stage; or when, at the conclusion of the countrymanqué exercise "Papa Was A Rodeo", nonchalantly twirls a lasso of smoke with his cigarette. It may not be much, but when songs are this strong, there's no real need for anything more demonstrative. Sometimes, understatement speaks louder than a Marshall stack turned up to 11.