'BEFORE rock'n'roll, the big thing was sheet music. Then came the vinyl explosion. And now dance music has metamorphosed, and left rock and its iconography behind. There's just no comparison between mainstream pop and the cutting edge of dance. They are consumed in a totally different way,' says David Davies.

The point of consumption tonight is the Omen, a stark, industrial night-club in Frankfurt. For Frankfurt is the home of German techno, the birthplace of the hardest, most uncompromising dance music ever made. Mr Davies is editor of Mixmag, a London-based magazine that rivals i-D and The Face as tipsheet for the sharp end of club culture. The December issue carried a five-page article on German techno and its latest incarnation, 'trance'.

Mr Davies expounds his cultural theories at the top of his voice, over a noise that might best be described in architectural terms. For Frankfurt is the birthplace of the hardest, most uncompromising dance music ever made. Towering, massive and meticulously planned, the techno is anti-jazz. The beat is a rigid steel frame with bass notes punched into it like white-hot rivets, and occasional snatches of melody on the surface. Were he alive to hear it, Wagner would wet himself.

The air is hot and thick, the walls are dripping. The Omen has no air-conditioning and little ventilation. In the summer, with 800 dancers drenched in sweat as they thrash across the dance floor, the resident DJ, Sven Vath, takes regular hits on an oxygen mask in the DJ booth. 'It's the only way he can work without fainting,' says Matthias Martinsohn. Five years ago Mr Martinsohn, Mr Vath and Michael Munzing bought a trashy mainstream disco called Vogue. They gutted it and created the Omen. Two years ago they began playing hard-core techno, although Mr Martinsohn is quick to dismiss the 'birthplace' tag. 'Anyway,' he says, 'the techno scene has peaked now, and we're looking for a new musical trend.'

Mr Martinsohn knows about musical trends. He and Mr Munzing are, respectively, the MD and senior producer of Logic Records. In 1990, under the guise of Snap], they released 'The Power', a phenomenal dance record that went to number one all over the world, making them multi-millionaires. Their latest Snap] record, 'Exterminate', is number two across Europe, outsold only by Whitney Houston's ballad.

The crowd roars as Vath snatches the beat from underneath them, leaving only an 'ambient' throbbing pulse. Wide smiles greet this sudden release, limbs are suddenly loose again, but the bodies keep moving. From this rhythmic limbo he will take the dancers back up, over several hours, before repeating the process.

Forget song structure, it is an irrelevance. Trancers do not care for tunes, either, or lyrics or performers. Trance is dance floor music, made by DJs or trancers. There are no lead singers, bass players or drummers. Pop icons are obsolete here. The only lyrics are sly, oblique jokes, such as the throbbing track with the robotic voice that asks, deadpan, 'Who . . . is . . . Elvis?'

'The trick is to pace and lead,' according to Guy Nisbett, 25. He designs virtual environments, or 'virtual reality'. He has designed a virtual night- club for Philips, who will market it on CDI, or compact disc interactive. Pace and lead? 'They pace you with one rhythm, then lead you deeper down with another that runs across it. Then that rhythm becomes the pace and it happens all over again. Before you know it, you've lost the plot completely. That's trance.'

A fan of 'intelligent techno', he flew out here on a whim 'to see what's happening on the trance tip'. For work? 'No, pure pleasure,' he says, laughing. Others have come from Cologne and Dortmund, and there are two coachloads here as well, one from Copenhagen, another from Amsterdam. In immaculate English the Dutch kids extol the virtues of the club and Sven Vath, whom they regard as the godhead of the underground dance scene. The Omen, you gradually realise, attracts a different kind of club crowd. A little more fanatical than most.

Even the drugs are different. Eschewing Ecstasy or cocaine, some trancers favour so-called 'smart drugs' such as choline or vasopressin, which supposedly stimulate the brain but have no 'come-down'. However, Mr Martinsohn has no time for drugs, smart or otherwise. 'Anyone found using drugs is ejected and barred. But you can never completely separate night-clubs and drugs. You can't watch 800 people to see who uses the toilet cubicles.'

Around 1,200 young people will pass through the Omen tonight, some departing for the even larger, louder and infinitely weirder Dorian Gray, a 2,000-capacity techno club underneath Frankfurt airport. Most, though, are here for Mr Vath's return journey, all the way out to the edge of consciousness and back again. The Omen closes at 8am, unless it is a great party, says Mr Martinsohn, in which case 'we just keep going'. Not bad for DM12 admission.

'Frankfurt is a trance factory on overtime at the moment,' according to Mr Davies, a regular visitor. 'It's the capital of

Europe's underground dance scene.' After his four-hour set, DJ Sven will fly to India and on to Goa. There he will be able to dance to much the same music as he played tonight.

India, underground music, new drugs, altered states of consciousness . . . isn't all this a little familiar?

'Yeah,' grins Guy, 'only this time we have the technology.'