They're pop's other brothers- the shy ones who don't make the gossip columns. So, asks Alex Bellos, how come Orbital's electronic dance music has the stadium-filling potential of Britpop?

As musical brothers, Paul and Phil Hartnoll are as far from Oasis's rock'n'roll siblings as can be imagined. Noel and Liam Gallagher argue and fight. they are professional loud northerners - obscenely arrogant, wonderfully charismatic and now intimidatingly famous. Les freres Hartnoll, on the other hand, never argue, let alone fight. They're quiet, sensitive, southern and, most distinctively, completely anonymous.

Yet in their own subtle way, the Hartnolls have been as successful as their Mancunian alter-egos in stamping their footprint on the face of British pop. As the electronic duo Orbital, they were the first band to show that dance music could not only equal rock as a live experience, but be much more exciting. Together with the Prodigy and Underworld, they are the founder members of what i-D magazine this month calls "the elite rank of stadium-filling, unit-shifting music press-adoring dance aristocracy".

The similarities between these bands are that they were all born from Ecstasy-fuelled rave culture- Orbital are named after the M25, the Sunset Strip of acid house parties- and have kept their credibility as that scene has become mainstream. Their differences: both the Prodigy, whose single, Firestarter, was recently number one for three weeks, and Underworld, whose album entered the chart at number two, still fulfil the terms of their original dance mandate. Orbital's trajectory is more bizarre: their fourth album, In-Sides, which is out this month, is a music box of odd sounds, robotic rhythms and swirling melodies- it's pure Orbital, but it's certainly not dance music any more.

Not that the crowd at Leeds Sound City festival, where the Hartnolls headlined last Friday, seemed to mind. It was the first rehearsal for a tour next month; there were none of the customary visuals, no 'Hello Leeds' banner, just two nerdish guys barely visible behind a monolith of computer equipment. By their own admission, "It's not much to look at," yet they had the packed hall in the palms of their hands.

This is Orbital's greatest irony. They make no effort to be exciting, apart from usually having screens showing random images, yet are widely rated as supreme performers. Their moment of truth was the Glastonbury festival in 1994, when the organisers gave them the coveted final Saturday night slot on the second stage. The now legendary performance went down with many critics as the musical high point of the year. In 1995 they were promoted to Glastonbury's main stage and were roundly judged to have put on a better show than both Oasis and Pulp, the headline acts.

John Peel was one of the first DJs to enthusiastically endorse the band: "There are strong arguments about computer music not having any soul. They have demonstrated that you can do it. Despite being theoretically mechanical, it doesn't sound mechanical."

Liam Howlett, of the Prodigy, believes Orbital were crucial in bridging the gap between rock and dance music. After the rave scene went underground with the introduction of anti-party legislation, he says, a lot of people went back to seeing live bands. " It was quite brave of the Glastonbury promoters to put Orbital on. But it was a really good move for the whole dance scene. Orbital's stage show is not that exciting, but it is different to four guys in a band, which is not really very exciting either."

Part of Orbital's success live, and a way they have influenced other electronic bands, is that they have lead the way in truly playing live rather than miming to backing tracks. Every gig is improvised from start to finish.

Paul, aged 27, programs in hundreds of sequences which they can then use as an artist might use paints. "On stage it's like juggling all these sequencers and deciding when to punch something in and when to take something out, what sound to use and how to mix it in the desk. People are more inclined to connect electronic music with purity and cleanliness and everything being in the right place, which isn't the case when we play live. That's the reason it works. It sounds rough and ready and raw."

Even though the Hartnolls have sought anonymity with the passion that most pop stars seek stop-you-in-the-street fame- they stood in the audience during the support bands last week and no one recognised them- their trainspotterish personalities have helped gain them a wide audience.

Push, editor of Muzik magazine, says that, like Oasis, merely the fact that they are brothers makes people interested. "They may just be two bods behind loads of electronic gear, but so are most dance acts. Being brothers gives them a humanness most electronic bands don't have. "

Phil, aged 32, is the eldest, quietest and baldest. He's married to Rachel and they have two sons, aged eight and five, and a pet dog. They live in north London, only a few miles from Paul. Nearby is their recording studio, which keeps alive the spirit of the Sevenoaks bedroom where the Orbital story began.

In the late eighties, Phil, then a labourer, and Paul messed around making music on computers. A friend who was starting up a label heard a track, Chime, and released it. In 1990, it reached number 17 in the charts and they appeared on Top of the Pops.

Since then, only one other single has reached the top 30, although three albums have done well, with 1994's Snivilisation reaching number four. Their second album was recently selected as one of Mixmag's 10 best dance albums of all time.

When asked to describe their musical relationship, they say that Paul programs more, but there is no typical "creative tension" they feed off. They rarely disagree, and never feel they make compromises with each other.

Stadium rockers perhaps, but the brothers have never embraced the rock lifestyle: "It just gets really boring very quickly," says Paul, who adds that the most exciting member of their touring entourage is a vegetarian chef. Paul adds: "I like meeting other bands, but that's like being into model railways and meeting other model railway enthusiasts."

They don't have their pictures on albums because they want "The music to speak for itself". Even their one gimmick, wearing glasses with lights for eyes, came out of a practical need- they couldn't see their computers properly on stage. Now their fans wear them in their masses.

Orbital's latest music reflects the fact that they don't really go to clubs any more and are much more interested in other influences. They recorded a track to go with a Sony computer game last year and hope to move into soundtracks. Paul has even bought a guitar. " I want to get MTV back one day for asking us to do 'Orbital Unplugged'. I'm determined to learn how to play Chime on the acoustic guitar. Do the camp fire remix. That'll show them."