Avon calling

New Orleans, Memphis, Liverpool, Seattle... Bristol? If you believe in the theory of site-specific popular music, of musical movements that are geographically determined (and in the mysterious power of ports), then the Avon is the latest river to follow the tides of the Mississippi and the Mersey in beaching up a revolutionary new musical form. The trip- hop sound of Massive Attack, Smith and Mighty, Tricky and Portishead (and that's just the first wave) has helped to make British dance music perhaps the most influential pop movement in the world today, for discerning listeners at least. And while the Bristol pioneers may still be in advance of mass public taste, just as any avant-garde should be, their example is being translated into mega sales by the likes of Everything But The Girl, with rock dinosaurs such as Tina Turner and U2 (who threaten a "dance" album as their next release) following in their wake. All this from a city that can't even manage a decent football team.

It is, admittedly, an unlikely scenario: dance music that you don't dance to, produced in the main by non-musicians, in a city whose only previous claim to pop fame was a few novelty singles by toothsome pianist Russ Conway in the days before the Mersey sound swept his like away forever. In the Sixties, while Liverpool had the Beatles, Manchester the Hollies, Birmingham the Spencer Davis Group and Newcastle the Animals, Bristol had, well, no one much... unless you count those dedicated regionalists Adge Cutler and the Wurzels.

It was at least partly because Bristol remained such a tabula rasa of rock, with no real music business structure to speak of, that allowed the stars of the present scene to emerge with their own sound so stylistically intact. The history of the city had its part to play, too. A pre-industrial capital of the provinces grown rich from trade with the New World (including the trade in slaves), Bristol has a prideful complacency about its laid- back ways that is second to none. When, in the Fifties, descendants of those slaves arrived in the inner-city suburb of St Paul's to seek their fortune, a kind of Notting Hill of the soul was established, with Jamaican country manners meeting West Country cider-head culture head on.

With few local models to conform to, other than the pervasive influence of reggae sound systems and the examples of early Eighties' funk-inclined punks like the Pop Group and Rip Rig and Panic, the current Bristol artists developed largely at their own, famously slow, pace. The spark that was to ignite them came from American hip-hop, which in Bristol was appropriated not just as music but as part of an integrated subculture of beats and attitude, art and dance, eagerly lapped up by the old slave port's mix of black, white and mixed-race kids. Providing the social context was the aftermath of the St Paul's riot of 1980, when Bristol's inner city erupted in the first and most shocking of the decade's civil disturbances.

Despite claims to the contrary - not least from the artists themselves, who hate to be lumped together - the Bristol sound does exist. I've got proof. In the summer of 1985 the Arnolfini Gallery in Bristol put on a show of graffiti art, with the artists - including 3-D, aka Robert Del Naja, later of Massive Attack - spraying directly on to the gallery walls. The work was perhaps a little disappointing, its raw energy losing something between the institutional context and the rather porous quality of the walls, but for one night the hip-hop sound-system crew to which Del Naja belonged - the Wild Bunch - were invited to put on a jam in the main downstairs gallery, and I videotaped it for the Arnolfini's archive.

Looking at the tape now is like scanning through a quaint old historical newsreel. There, gathered around the turntables, is the Wild Bunch: Miles Johnson and Nellee Hooper cutting up tracks, Grant Marshall picking out the next record as the very young Andrew Vowles stands by his shoulder looking on. In the audience are the Pop Group's Mark Stewart, the producers Smith and Mighty, Tricky and, on his first trip to Bristol without his mum, the barely adolescent Geoff Barrow, later of Portishead. As the Wild Bunch mixed their eclectic choice of records - a permutation of soul, rap, reggae and funk - kids dressed in hooded sweat-tops break-danced dangerously around the gallery and occasionally a group of adult Arnolfini regulars walked past the camera like safari-jacketed anthropologists on a field trip.

Now, Del Naja, Marshall and Vowles are Massive Attack, the group whose 1991 album Blue Lines has been described by Radio One's Pete Tong as the best album of the decade; Miles Johnson, the Wild Bunch's leader, lives in New York, where he is working once again with his protege, Tricky. Nellee Hooper, who went on to form Soul II Soul with Jazzie B, is probably the most in-demand record producer in the world, largely as a result of his brilliant work with Bjork. Geoff Barrow's group Portishead made a debut album in 1994, Dummy, that has sold more than 1.5 million copies worldwide. Smith and Mighty still remain the least commercially successful of the lot, but they've more than made their contribution: you could argue that they pretty much invented jungle, the first fully naturalised form of British electronic dance music.

The Pop Group's Mark Stewart is still an outsider, though his influence on the scene has been crucial. In 1985, he booked the Wild Bunch for a sound-system battle at London's first rap club, The Language Lab, through which Soul II Soul was born when Nellee Hooper met Jazzie B; he also introduced the Scandinavian punk Neneh Cherry to his Pop Group colleagues Gareth Sager and Bruce Smith, with whom Cherry started the group Rip Rig and Panic, and he made probably the first recording of the Bristol sound, when he took a Smith and Mighty version of Erik Satie's Gymnopedie No 1, set it to some words from West Side Story's "Somewhere", and put it on his 1987 solo album.

Later, Neneh Cherry got members of the Wild Bunch to work on her first album, Raw Like Sushi, and then enrolled Geoff Barrow to write music for the follow-up.

Massive Attack came about after Cherry and her husband, Cameron McVey, signed the remains of the Wild Bunch to their management company and got them a record deal with Virgin, from which Blue Lines emerged. On Cherry's latest album, Tricky - who first came to prominence as a rapper with Massive Attack - is featured. Tricky's new album includes tracks produced by the Wild Bunch's Miles Johnson.

Despite the incestuousness of the musical relationships, or possibly because of them, the notion of a handy, catch-all Bristol sound does not go down well today with the participants, many of whom are no longer on speaking terms. Miles Johnson, whom many people see as the most creative force in the Wild Bunch, has not talked to Nellee Hooper or the members of Massive Attack for eight years.

Bristol today is full, too, of people who had a hand to play in the early days but who never got the breaks their successful peers managed to engineer for themselves. The latest wave of Bristol artists includes the Full Cycle Records team of drum and bass producers such as Roni Size (soon to have his own album on Polygram's Talking Loud label), as well as second-generation sound-system producers such as Way Out West and Henry and Louis, and real bands like the hotly tipped Crustation, and Aerial, whom Massive Attack have signed to their own label, Melankolic.

With Tricky's new, defiantly uncommercial, album about to hit the shops, Portishead's follow-up due shortly (though "shortly" can, in Bristol, mean a very long time), and Massive Attack's third, reputedly punk-inspired, album set to appear sometime next year (only their third album in six or seven years, a period as long as the Beatles' entire recording career), the Bristol sound is set to keep on going, through inertia as much as anything, for quite a while yet. Which allows even more time for everyone else to catch up with it. And, as in the wonderful early singles by Smith and Mighty, the Wild Bunch and Massive Attack - all now unobtainable, though Massive's label might re-release them soon - there's an awful lot of catching up to do, before the juggernauts of U2 and the other imitators make us forget where the new British dance music - the kind you don't dance to - came from n

`Straight Outa Bristol: Massive Attack, Portishead, Tricky and the Roots of Trip-Hop' by Phil Johnson, is published by Hodder and Stoughton, price pounds 9.99.