The Chemical Brothers: 'We want to immerse people in something completely different'

It is less than 48 hours since the Chemical Brothers finished playing the last of four nights at the Roundhouse in Camden, north London, and over mineral water Ed Simons is thinking about how he feels now. "It's strange not to be in that little rhythm," he says, "where you're building up to a performance in the same place each night. You know what to expect, but you still get nervous.

"It was how I've always imagined it must be like to be in an actor in a long-running play," he continues, "or going to work in an office each day."

In fairness, it's been a long time since the Chemical Brothers had to consider such a fate. Beginning with Exit Planet Dust in 1995, their six albums have all reached the top 10 in the UK (the last five hitting No 1) and no other band following the Big Bang of rave has known such success. It's led them to where they are now, contemplating what to have for lunch in a smart restaurant just down the road from the pub where they first DJ-ed after moving to London from Manchester University in the early 90s.

"Now, does anyone fancy sharing the charcuterie platter?" Simons asks. His partner of 15 years, Tom Rowlands, does. It's all very genteel and some distance from the mind-expanding experience of the music, which is also at odds with the pair in person. "If we were walking down the street carrying record bags," says Simons, "then we might get noticed, but not otherwise."

It's been said before that these superstar DJs, as they called themselves with no little irony on their 1999 hit "Hey Boy Hey Girl" – both dressed in black polo shirts today – are actually quite dull, but this misses a couple of points. First, that they've stayed true to one of the ideas that seemed so liberating when they emerged: the idea that in dance music the audience would be the star of the show. Second, the sound that the Chemical Brothers create and the reactions that it provokes can be quite extreme, as I can attest given that, on Sunday night, about nine minutes in, one member of the audience threw up on my back. This provokes ribald merriment as well as concern. "How grim," Rowlands says, adding considerately, "you should have taken a new T-shirt from our merch stall."

The shows at the Roundhouse were staged to showcase their new album, Further, a deeper, darker record than its predecessors, which spurns the assistance of guest vocalists, but was conceived with a new visual show created by long-term collaborator Adam Smith in mind. "It was a bit daunting," says Rowlands, "because normally when you see a band and the singer says, 'Here's a new one!', the question is, 'Anyone want a beer?' I'm guilty myself. But when you DJ, people are obsessed by what you've got that's new, so this was a way of saying, here – have an hour of it."

It's appropriate that they chose the Roundhouse, given its heritage as home to the original 60s happenings when bands such as Pink Floyd fused psychedelic sounds and imagery. "It's a good tradition," says Rowlands, "but I'm sure it felt then like the verge of a new dawn and that's very much disappeared. What we're trying to do is give a sensation, a feeling… to immerse people in something completely different. Even listening to music now, it's just skip, shuffle, shuffle, and this record flies in the other direction."

"Just getting people out of the house and getting them together," says Simons, "that fills me with quite a lot of joy. Even if someone being sick on your back isn't ideal…"

Part of the challenge as Simons and Rowlands approach 40 is to stay relevant, but while Rowlands says it's nice to know what's going on, he insists they've never made music as a conscious reflection of anything else: "We've never said, drum'n'bass is really big, let's make a drum'n'bass track." But the duo still DJ and keep "one ear open trying to understand how people do things".

"There's a producer called Popov," Rowlands continues over his chicken paillard. "It's mind-numbing music and if you hear it in the day you'll think, what's the point? But there's something weird in its construction that sends people insane at four in the morning and we want to work out what the secret thing is."

Is it possibly the case, I wonder, that at 4am the audience is in a particularly receptive frame of mind that might be chemically induced?

"People do what they do," Rowlands demurs, "and what they always have done." Their name notwithstanding, the duo never seem to have embraced the more debauched elements of rave themselves. "We're straight-edge kids!" he half-laughs, half-deadpans.

"I've noticed that there's much less druggy energy in the clubs," says Simons. "What people do to our music is not any of my business. It would be churlish to tell them how to behave."

"You read that people are still taking drugs," Rowlands adds, "but whether it's like it was when rave exploded, between 1988 and 1992 I don't know. Perhaps it's just that rave culture is so far assimilated into youth culture now."

Nonetheless, I say, I suspect that whoever it was who slightly took the gloss off my evening on Sunday was suffering from pushing the envelope too far.

"Or it could have been a dodgy prawn someone ate," Simons says judicially.

Does settling down mean losing their edge? Since having children, the married Rowlands has lived in bucolic east Sussex. "Our nearest neighbours are a shepherd and a farmer," he says. "They know what I do, I think; they haven't expressed any displeasure."

Simons, who is single and whose only brush with the paparazzi came during a relationship with Lily Allen, drives down regularly to potter with Rowlands in his studio. This is filled with synthesisers and drum machines. "I like the imperfections of old synths," Rowlands says, "their foibles.

"Electronic music can be celebrated for being tight and orderly," he continues, confessing that one of his highlights was sharing a lift to the stage with Ralf and Florian from Kraftwerk at a festival in Belgium. "But we want to create the sense of machines sweating or creaking and falling apart. There is a generation who make music on their laptops, but I like old instruments."

It's often asked what the Chemical Brothers actually do on stage, but Rowlands explains that they control the arrangements of each track – "Dissolve" from Further, for example, is "broken into 16 parts, and within that there are many possibilities, just with the mixing desk. We might have something completely different that we came up with in the soundcheck running beside it. On Sunday night, we threw away sections of songs to do something else before returning to them. We want to sound as if we're only half in control."

It seems strange to him, he says, that when electronic bands have hits they so often succumb to record company pressure and use a live drummer to replicate their sound for TV. "I wonder if that mythical drummer would have done the 15-year stint!" says Simons.

This long into their career, the secret of their relationship does sound slightly mundane. "We've had a lot of good things happen and we've made a lot of good things and that sustains the friendship," says Simons.

Later, I speak to their visual collaborator Adam Smith, who says that while the budgets he's been given have marginally improved (the films for Further, available on the accompanying DVD, were partly shot at Pinewood), Tom and Ed haven't changed – that they're still "lovely… a bit older, but they still giggle and act like pair of juveniles before a show".

"We just like each other," says Rowlands, "we enjoy each other's company. We used to live on the same street and we used to go on holiday together and we don't do that any more." He drinks his coffee and concentrates on the bizarre jazz playing in the background. "I wonder how it's put together," he says.

Simons returns from a fag break. "Longevity for its own sake is meaningless; it's not hard to stick around," he says. "To keep making records that mean something to people is the difficult bit."