The question comes off like an old "Monty Python" gag. What musical group in Britain is more popular than Paul Simon or the Ting Tings? The Monks of Stift Heiligenkreuz. Several weeks ago, a group of Cistercian monks who live in a 12th-century monastery near Vienna, who wear cowls and wake at 5 each morning to pray in Latin, made a little music history when their album of Gregorian chants soared up the pop charts and landed at No. 7. At the same time, the CD, which is not yet released here, found its way to the top spot on the U.S. classical chart last week, thanks to feverish downloading on iTunes. Father Karl Wallner, the 45-year-old monk who has been at the monastery since he was 18 and is charged with answering media inquiries—"they call me 'press monk,' that's very funny," he says—had just said goodbye to two television crews and spoke with NEWSWEEK via his cell phone.

Gregorian chant is popular among young people because "there's a big harmony with those melodies." Indeed, at a time when the Roman Catholic priesthood is suffering diminishing vocations in the Western world, Stift Heiligenkreuz has an abundance—28 young men have entered in the past five years. Wallner thinks it's because of the chant.

The success of the monks' album is not entirely a gift from God, as Wallner would have you believe; it's more a dovetailing of smart marketing by a classical-music company in Britain and surprising technological savvy on the part of the monks. Last winter, noticing a surge in sales of chant as well as the runaway success of the futuristic, sci-fi videogame Halo—which uses chantlike melodies throughout its soundtrack—Tom Lewis, an A&R executive at Universal Music Classics, launched a kind of "Pop Idol" contest for Gregorian chant, which he advertised in Catholic papers throughout Britain.

Father Karl heard about the contest via e-mail and, on behalf of his brothers, he entered it at the last minute using a slickly produced YouTube clip—which the monks happened to already have online as a kind of virtual tourist attraction. "They made, quite simply, the most beautiful sound of all entries received," writes Lewis in an e-mail. "As well as singing we were also looking for enthusiastic ambassadors for Chant—an element of star quality, if you like." Seventeen of the Heiligenkreuz monks recorded the album in a chapel known for its acoustics. They sing parts of the Divine Office, prayers for the dead and some bonus tracks. Peter Jeffery, a music historian at Princeton, likes this album better than the one produced by Spanish monks in 1994. "I do find it appealing," he says. "I feel like I should buy it."

Meanwhile, back in Seattle, the man who composed the soundtrack for Halo finds the whole phenomenon very amusing. A graduate of a Christian college, Marty O'Donnell belonged to an early-music ensemble in graduate school. He played the flute and recorder and sang Gregorian chant. When Halo's developers told him the game was a "sci-fi, futuristic, epic place with some ancient mystery," he immediately thought of chant.

The chant O'Donnell composed for Halo is not authentic—it has no Latin words, for example—but the kids who play the game don't know the difference. "I know that my audience a lot of times is teenage males … and they don't necessarily have a huge exposure to a lot of musical styles. When I do chant or solo cello, they're going to hear it as something unique and different, even though it's not." On the day he spoke to NEWSWEEK, O'Donnell had e-mailed news stories about Heiligenkreuz to his wife, who'd written back with a quip: "Talk about the tail wagging the dog." You could hear the smile in his voice.

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