Cultural commissars met their Waterloo in Abba

Forty years ago this week, a song was performed on stage at the Brighton Dome in the UK that changed the history of pop music.

Not that anything historic seemed under way at the time: the four Swedes jumping about in Euroglam spacesuits seemed to be the type of Eurovision Song Contest winners who would entertain for an evening and then drift into obscurity.

It was unthinkable, listening to the heavily accented women ("Napoleon deed surrenda"), that the world had just witnessed the launch of a global phenomenon.

The song, Waterloo, now, literally, has its own chapter in the history books. It not only launched the career of the world's most successful pop group, the Beatles excepted, but also a country's pop industry.

And the demand for Abba continues today - so much so that their greatest hits album, Abba Gold, overtook Sgt Pepper'sLonely Hearts Club Band a few months ago as the UK's second-biggest-selling album. Waterloo can now be seen as a kind of musical big bang whose consequences are still unravelling.

Like all overnight successes, Abba had been trying to get it right for years. They were rejected as Sweden's 1973 Eurovision entry with their song Ring Ring.

But the track sold well abroad, encouraging Abba to come back in 1974 with a number intended to break the mould by eschewing the usual mid-tempo ballad form and delivering a musical thunderbolt.

Waterloo was written while the band's two men, Benny Andersson and Björn Ulvaeus, were jamming together on the piano. They did not agonise about lyrics to pierce the soul of a continent. They had a great tune and needed a three-syllable title that would not need translation.

Stig Anderson, the group's manager, thought about "Honey Pie", but the Beatles had done that. He came up with "Waterloo" while thumbing through a book of quotations. It was perfect for Eurovision, bound to please the Brits. He knocked together the words in an afternoon.

Waterloo would be sung by Andersson and Ulvaeus's respective partners, Anni-Frid Lyngstad and Agnetha Fältskog, and they would try to stand out in spangles and platform shoes. The outfits were garish for a reason - under Swedish law, tax relief was offered on costumes as long as they were so outrageous that they could not be worn on the street.

It fitted their strategy anyway: for the first time, a jury of ordinary Swedes was choosing the Eurovision candidate and Abba wanted to wow them. This worked as well in Stockholm as it did in Brighton. Waterloo became the greatest ever Eurovision success.

Sweden's music establishment seemed shocked at Abba's victory. Such a reaction can only be understood by the ideological challenge the band presented to the prevailing l eft-wing musical orthodoxy of the time.

Socialistic Sweden had embarked on a cultural strategy devoted (among other things) to mitigating "the negative impact of commercialism". Abba's success posed a conundrum to Stockholm's cultural commissars: if Waterloo and Mamma Mia! were so trashy, the lyrics so absurd, why did the people like them so much?

Dark theories were advanced about what, precisely, Abba represented. A Swedish composer, Jan Morthenson, spoke darkly of its "totalitarian culture".

To Johan Forns, a Marxist critic, the band's success was a sign of a sick capitalist society. But the blame, he said, ought to lie with "the society that causes people to have no energy, or desire, to do anything other than listen to Abba after coming home from work".

It seemed the workers of the world were indeed uniting - but under Chiquitita rather than the Internationale. The Soviet Union tried to limit such corrupting influences by placing quotas on imported pop. In 1976, Poland used up its entire allowance on 800000 copies of Abba's album Arrival.

The disdain in which critics held pop songs was such that few recognised what Abba was doing right. They took their music more seriously than anyone. Their studio, Polar Music, became the Swedish Abbey Road.

They would work and rework harmonies and riffs. A memorable chorus was not enough: they needed a catchy motif and a recognisable intro. The "oom pa-pa" in Super Trouper, the "ah-haaa" in Knowing Me, Knowing You - these are the things that made Abba's music so addictive.

Such tricks would be copied by artists from the Sex Pistols to Madonna. Abba Gold is now in one in 10 British homes, more than any album except Queen's Greatest Hits. By no coincidence, Queen is about the only band less fashionable than Abba, although, at a wedding reception, you are far more likely to hear Dancing Queen than any songs by Queen.

Abba's songbook has become a kind of common currency, cutting across boundaries: secular hymns for the Western world. The 2008 film, Mamma Mia! , had A-list actors murdering two dozen Abba songs. It was panned by critics, yet became the highest-grossing musical in Hollywood history. Yet again, it was a triumph of popularity over fashion .

And that is why, 40 years on, we are still thanking Abba for the music. - ©The Sunday Telegraph, London