The Aquarium, London

"Do you like my tight sweater?" the singer said to the keyboardist. "Inspired!" whispered the keyboardist to the singer. "Meet me later in the studio!"

It was this flirty encounter at a party, or something like it, that romantically and professionally united the leading lights of , Roisin Murphy and Mark Bryson. And it is Murphy's skinny, ribbed top that prompted the delightfully absurd name of their immensely underrated 1995 debut album Do You Like My Tight Sweater?

(it means "milk" in Russian) are continually being compared to Portishead, clearly to the disdain of both bands. Portishead's programmer, Geoff Barrows, is reputed to have stormed into a gig wearing a T-shirt bearing the insignia "Accept no imitations".

There are certainly superficial similarities - both bands have enticingly irreverent female singers and an instantly recognisable sound - but what separates from their trip-hop peers is their sprawling experimentalism combined with the singer's singular theatricality. Portishead may have honed the agonised approach to perfection, but stylishly encapsulate a vast array of moods and styles.

Now backed by a drummer, a keyboard player and a stockpile of new tracks, have lost none of their crooked humour and they are still given to confounding their admirers. We are greeted by a foreboding and utterly indecipherable a cappella incantation that stops the boringly trip-hoppy audience dead in their tracks. "If you think you're here to dance, think again," Murphy seems to say, as she launches headlong into "Blink", an elaborate jungle- driven track from their forthcoming second album, I Am Not A Doctor.

The sheer force of Murphy's voice often renders her words unintelligible, but the nonsense-verse quality of her lyrics means that somehow it doesn't really matter. Eerie elegies or childish twaddle, they are peculiarly seductive.

Clad in black, this art school drop-out turned dominatrix cuts an imposing figure. The flouncy feather in her hair may be intended as a softening touch but, looking at her wild eyes and flashing teeth, you might be forgiven for assuming that she had personally caught and plucked its original owner.

's new material is sometimes abrasively experimental and mind-bogglingly complicated, juggling clashing rhythms and seemingly irreconcilable sound effects. A couple of nervous glances between Murphy and Bryson bear out the fact that they have set themselves a hard task, but they need not have worried. As Brydon's grooves traverse jazz, hip-hop, funk and Eighties electro, Murphy is by turns scorched, saucy and silly. Her kooky mannerisms are Siouxsie Sioux, her crazed countenance Grace Jones, while her throaty, feline drawl is pure Eartha Kitt. This arresting array of vocal identities would have made her a perfect storyteller on Jackanory, scaring children out of their wits with her witch's voice.

Moving into the more familiar territory of "Fun For Me", Murphy stalks up and down the stage, waving her arms about and hissing the words with acidic glee. The crowd, still trying very hard to dance, roar their praise.

But Murphy can also be disarmingly sweet. As she steps out of her chosen guise inbetween songs, she demurely mutters her thanks and breaks out into a beatific smile. Not only is this fiery lady a dazzling performer, you could probably take her home to meet your parents as well.

Fiona Sturges