Ten years ago I spent an evening with German relatives in a vast beer hall housed in a tent overlooking a snowy valley. The beer was good, but the musical accompaniment - bouncy, folksy brass- and-accordion fare played by four moustachioed men wearing lederhosen - was a violent assault on good taste. Or so I thought until I discovered that my companions were immersed in a powerful trance, tapping their feet, hugging strangers, and raising their tankards skywards every 20 seconds.

This was my first brush with Volksmusik, a melodic form whose mysteries are beyond the reach of anyone not born in Germanic culture. To the unitiated, it is the pinnacle of kitsch, bucolic nonsense put to simplistic, sickly sweet music. It is the tonal equivalent of wooden cuckoo clocks.

And yet there is something fascinating about the genre. Literally translated as ”folk music”, it was born in beer halls and the market places of Alpine villages. The stories it tells - about romance, longing, nostalgia and, above all, love for one’s Heimat [homeland] - are as old as the German language itself. But what marks it apart from any other strand of folkloric songs and tunes on the European continent is the capacity it has shown to permanently reinvent itself, with young new talent emerging all the time.

Few other genres can boast as big a media presence, including prime-time television slots, talent contests and its own Golden Globes, the Grand Prix der Volksmusik. And far from being dead, the style is mutating, forever borrowing from a vast pool of inspirations, including pop, samba and techno - all of which are given the rustic treatment.

Unsurprisingly, it is among the German-speaking world’s biggest music markets, with an audience topping 10 million in Germany alone. Its enduring success is unique among other forms of European folk music, and perhaps only comparable to that of country music in the US, with its mixture of traditional roots and modern influences.

Although the charms of Volksmusik continue to elude me, its astonishing vitality has never ceased to arouse my curiosity. What, I wonder, could lie behind the magnetic power of those innocent ballads about true love, Alpine summits and cowbells? The answer lies with a stocky man with silver stubble and droopy features that seem incapable of producing a smile. Hans Beierlein, who describes himself as a ”wholesaler of entertainment”, is a legend in Germany’s music business. Without him, Volksmusik would almost certainly have tipped into extinction decades ago.

In order to understand what this Bavarian - often referred to as the country’s most successful independent media manager - has achieved, it is worth recounting a 30-year-old anecdote. One evening in 1975, watching television footage of a rally in the German Democratic Republic, Beierlein conceived what must be one of the simplest and best business ideas formulated in the second half of the 20th century. Who, if anyone, he wondered, possessed the rights to ”L’Internationale”, the anthem of the workers’ movement that was being sung hundreds of times a day on the communist side of the iron curtain?

Beierlein’s research led to a socialist publishing house in France, which had inherited the song, written by a French revolutionary and put to music in 1888 by a Belgian woodcarver, but never collected any royalties. Beierlein managed to persuade the owners to cede him the German rights for $5,000. Within a few months, he had acquired ownership of the song for more than 100 countries - including the entire Soviet bloc - and began claiming payments from communist regimes across the globe. ”Left-wingers never understood the notions of rights,” he says, coaxing half a smile.

This was Beierlein’s first application of the recipe he would use again, five years later. He acknowledged Volksmusik as an underdeveloped genre with a huge following and no media presence - a bursting cow yearning to be milked. Beierlein was already well known as the manager of Udo Jurgens, one of Germany’s most famous crooners, and had brought the heavyweights of French chanson to Germany.

Using skills honed as organiser of the Miss Germany contests in the early 1970s, Beierlein embarked on making Volksmusik mainstream, cleaning it of its stigma as a popular but backward-looking sub-genre, and making it fit for the era of mass media. ”The music was there, but up to 30 years ago, it was taboo for the mainstream media,” says Beierlein of the highbrow contempt for Volksmusik that prevailed in the state-owned television networks of the time. ”But its audience was huge and completely neglected. Today, a good Volksmusik TV show can get six to eight million viewers. Only a World Cup final can beat that.”

Under his tutelage, television became Volksmusik’s first marketing platform, allowing it to attract younger talents. Today’s most successful Volksmusik TV shows were Beierlein’s inventions. At about the same time, he ”re-engineered” Heino, a well-liked Volksmusik singer who, because of his strange albino looks and persistent (but incorrect) rumours about his reputedly right-wing leanings, had suffered from a near universal media boycott.

Beierlein’s populist intervention earned him criticism from purists, who accused him of perverting folk traditions with snazzy marketing, synthesisers and sexiness. Asked to define the genre - a controversial exercise that still pitches traditionalists against modernists - he embraces a broad description. ”Volksmusik is the music of traditional values - friendship, loyalty, love, marriage, the terroir, God, nature. And musically, it is anything you can sing to - not just umpah-pa and tra-la-la. OK, it’s that, too, but not just that.”

Crucially, Volksmusik is also the music of the 26,000 fests staged in Germany each year, from the Rhine valley’s monumental carnival to Munich’s Oktoberfest, the world’s biggest folk fest, and the countless village and street festivals that dot the national calendar.

But what about the politics of Volksmusik? One reason the style is still looked down upon by the German elite of taste is its association with the political right. Is there a dark side to the genre’s obsession with the Heimat and milk-fed blondness?

”That’s nonsense,” says Beierlein. ”I had a poll of Heino fans carried out. It showed 80 per cent were social democratic voters and 92 per cent had a trades union membership. So, yes, it is about values, it is about keeping the world as it is rather than changing it. But it is apolitical in the sense that you could not run an electoral campaign on a Volksmusik agenda.”

It is a testament to the importance of Volksmusik that it consecrated what was arguably the first act of cultural intercourse between the two halves of Germany. Following reunification in 1990, sales of the genre were boosted as east Germans, who knew the tunes well from eavesdropping on western radio, began to purchase the music.

Sociologists have sought to explain the phenomenal success of Volksmusik in the late 1990s by the fact that it embodies precisely the kind of joie de vivre Germans aspired to in the dark years that followed the bursting of the post-reunification bubble. But with the economy now growing again and unemployment falling like a rock, are the days of Volksmusik counted?

Beierlein dismisses the suggestion. ”Somebody should write a book about what Germany would look like without Volksmusik,” he says. ”No Oktoberfest, no carnival, no Christmas markets, no football even. Forget it.”

Bertrand Benoit is the FT’s bureau chief in Berlin.