Zero 7 have been hailed by some as the new kings of chill-out, while being "a sort of lava lamp for the ears" to others.

They are both commercial success stories and critical victims of that paradox of modern music - that the more tasteful your sound, the less likely it is to register on people's palates.

Veterans of London's late-Eighties club scene and one-time industry tea boys, in 2001 producers Sam Hardaker and Henry Binns teamed up with vocalists Sia Furler, Sofie Barker and Mozez and made Simple Things, a warm blend of elegant jazz, subtle West Coast soul and laid-back electronica in which ethereal vocals and expansive synths drifted along on a gentle current.

The album went platinum, receiving Mercury and Brit nominations.

It was also, however, so soullessly smooth you suspected it had been produced via a Brita Filter. And, when it came to the follow-up, March's equally successful When It Falls, the lads did themselves no favours in their critics' eyes by failing to develop their sound. Except for drafting in another vocalist, Tina Dico, whose softly-softly vocals fit so perfectly with the chiming guitars and subdued brass on Home, it could have been the same album.

"To be honest, I think maybe I should've thought harder," says Binns, speaking on his mobile as he shops in HMV. He's taking advantage of their five CDs for £30 offer and buying a bunch of soul music which he's "probably already got". A very Zero 7 thing to be doing.

"With When It Falls especially, we were hiding away from all the attention we'd been getting," he explains, "and I was basically trying to write some more songs. Cosmetically, the two albums are very similar but we do now dress it up with some kind of psychedelic sound. That makes it a little less like straight-up 'adult contemporary'."

Unfortunately, it also makes Zero 7 sound a little more like Air - not a bad thing in itself but a bad move for a synth-wielding duo who've been dogged from day one by comparisons to the French artistes.

"With that first album, Air hit on something which I thought was magical," says Binns. "It was at a time just after Portishead, when you had these big beats but with this sound of damnation. Air came along and added these really sweet melodies.

"I do think we're different to them though. As the French do, classically, they have more of a facade. I've never worn an outfit - I wouldn't know where to start."

While Binns admits "I have got a soft palate" and that "I'm not afraid of easy listening", it seems Zero 7 are far from complacent about their city-slick sound.

It may have afforded them an unusually wide demographic, with audiences ranging from 15 to 45-year-olds but the time has come, he thinks, to "shake it up a bit".

"In a way I wish the records hadn't been as smooth," he confesses. "Sometimes you can refine a song so much that you can hardly recall hearing it.

"You're also in danger of falling into a bracket - which is exactly where we do fall - which somehow takes some of the soul out of the thing.

"That's why the live thing is absolutely essential - it does drive home who's written the songs and why they're singing it.

"It gives this very personality-less thing a personality."

Starts 6.30pm, Tickets £16, Tel 0870 900 9100