Writer and radio DJ Bart Plantenga sets out the answer in his book "The Secret History of Yodeling Around the World" which will be published early next month.

It's the first all-embracing look at the oft-derided art which echoes through cultures as diverse as the Bollywood soundtrack and the Pygmies of Central Africa.

"I couldn't believe no one has ever written a comprehensive book about this before," Plantenga told Reuters.

"There have been books about German or Swiss yodelling or about country music. But I can't believe there are 10 books on Britney Spears and nothing on something that is ages old," he
said.

Plantenga isn't a yodeller himself ("I've tried but I can't even sing"). He admits that most friends have greeted his book with a "bemused grin or a perplexed glaze," and is sanguine about how most yodellers feel they should rehearse out of earshot - in the shower, in their cars, "or in a studio lined with mattress-thick insulation."

But he'd stake his epiglottis on the fact that yodelling has had more influence on both music and popular culture than most people realise.

He decided to tackle the subject while working as disc jockey at a free-form New York radio station in the mid-1990s when he noticed how many artists were blending yodel samples
into the music he was spinning.

When he started his research "people came out of everywhere. It seems I have become an advocate for a forgotten minority, for all the yodellers who have been neglected or denigrated," he said. 

"I wanted to validate yodelling as something that has got into a lot of legitimate and/or other places where people have never bothered to look before"

DJ Bart Platenga

Yodelling and Yahoo!

Take Wylie Gustafson, the American country singer who has recorded eight albums but is best known as the voice of the Yahoo! Internet commercials. "Ironically he is more famous for this two seconds of corporate yodel than he is for his own records," Plantenga said.

Plantenga's book not only traces how the centuries old Swiss mountain call made its way into American country music but also looks at the lesser-known yodelling traditions in Hawaii, Mexico, New Zealand and central Africa.

Even while taking yodelling seriously enough, he light-heartedly packs his 300-page book with fascinating trivia.

Like the recipe for the Yodel cocktail, the online herbal medicine store called Yodel.inc.com, the Drake's Yodel - a hot-dog-roll-shaped piece of spongy chocolate cake filled with a cream substitute - and yodelling's place in the annals of sexual slang.

"I wanted to validate yodelling as something that has got into a lot of legitimate and/or other places where people have never bothered to look before," Plantenga said.

For those who consider yodelling more hop than hip, he reminds readers of the success of the 1970s Dutch rock band Focus and their ululating mega-hit "Hocus Pocus."

Yodelling has also been appropriated on occasion by rap (De La Soul), classical music (Rossini), hip-hop (the Fugees), rock (Kid Rock) and jazz (Leon Thomas).

Plantenga, who now lives in the Netherlands, says he would have preferred to call his book "Will There be Yodelling in Heaven?" because of "its allusions to loftier climes."

He doubts it will make the best-seller list - except perhaps in Switzerland. But he would be delighted if his book brings recognition to the hundreds of forgotten artists he has encountered during his years of research.

"It would be great if people decided to check some of these people out, like Kenny Roberts, and they were given record contracts or rediscovered," he said.