In a business that seems to demand "more of the same" for its very lifeblood, every new Elvis Costello project raises an unusual question: In which section of the store does it belong?

In a business that seems to demand "more of the same" for its very lifeblood, every new Elvis Costello project raises an unusual question: In which section of the store does it belong?

The multifaceted new wave survivor is about to provide another classification challenge with "For the Stars," a remarkable collaboration with the distinguished Swedish mezzo-soprano Anne Sofie Von Otter. Issued by Deutsche Grammophon March 19 in the U.K., the album is due from the label April 10 in the U.S.

"For the Stars" -- on which Von Otter interprets a broad swath of material occasionally accompanied by Costello, who produced and arranged the entire record -- eschews the classical crossover syndrome in two fundamental aspects. It could by no means be described as a mainstream pop project, and far from being some record-company contrivance, it's the result of a long, measured process by which these dons of different disciplines became confidants and then co-workers.

In his catalytic role, Costello nurtures Von Otter's subtle interpretations of songs by the Beach Boys and the Beatles at one end of the scale and Tom Waits and the Fleshquartet at the other, with material by Costello, Ron Sexsmith, Anna McGarrigle, and even ABBA pitched intriguingly in between. It is a formula as sure to fascinate the musically catholic as it is to confound dedicated followers of convention.

According to Von Otter, some people react to her Costello partnership with the attitude that "it's a great idea and they're looking forward to hearing the results. Others are skeptical and wonder why: Is there a strange reason behind this, i.e., money? They expect that it's just a product of the record company's 'dirty fantasy.'"

Far from it, "For the Stars" was born of sincere experiment -- one designed from a musical, not a marketing, impetus. "It's not a pop CD," Von Otter insists. "It's a cross-pollination between chamber music, pop, a bit of classical, and a lot of folk. When the two of us cook up something, it's bound to have a slightly different taste, and you don't necessarily need to call it something."

"'Crossover' is a word none of us likes to use," says Universal Classics chairman Chris Roberts. "But this to me is what crossover should be -- organic, convincing, honest, but also connecting music to a wider audience. We had very little to do with this -- and I'm not ashamed to say that -- other than giving them the support to shape the record way they needed to. We trusted them completely."

Before the pair ever met, Costello attended many of Von Otter's shows with his wife, Cait O'Riordan. After meeting the mysterious admirer who had been anonymously sending her flowers, Von Otter struck up a friendship with Costello that emboldened him in 1996 to compose the song cycle "Three Distracted Women" for the mezzo and the Brodsky Quartet (with whom he had taken an earlier classical detour from his rock path with the 1993 album "The Juliet Letters"). Joint live performances came next.

"I started out very much as a member of Anne Sofie's audience and a fan," says Costello, who listed her Deutsche Grammophon lieder disc "Wings In The Night" as one of his 500 favorite albums in last November's Vanity Fair. "Then we were introduced, but this idea of working together developed spontaneously. People were saying it before we said it."

For more than three years, Costello and Von Otter corresponded, swapping tapes and song ideas, before embarking on a dozen days of sessions that were extraordinarily productive, yielding 27 songs. Eventually, Costello had to make the switch from admiring fan to objective producer.

"You travel quickly," he says. "When you love somebody's voice, you can be quite in awe, and you wouldn't presume to make any comment. But this is such an utterly different type of singing [for Anne Sofie], and I know there are pitfalls for certain types of voices singing close to the microphone, singing certain types of repertoire. So we talked about these things openly -- there was no point keeping it until we were in the studio."

One of the hallmarks of Costello's production style is that while "For the Stars" contains the work of many renowned songwriters, they are often represented with lesser-known material in unique arrangements. For instance, Waits' "Broken Bicycles" segues into Paul McCartney's "Junk," with the melody featuring an improbable accordion embellishment from Benny Andersson of ABBA (which once recorded in the same Atlantis Studio in Stockholm where "For the Stars" was tracked).

Andersson also adds keyboards to an affecting version of ABBA's "Like an Angel Passing Through My Room," a song that has a certain classical aura. Roberts recalls, "Someone came into my office while I was playing it and asked, 'Is that a Schubert song?' "

Of working with Andersson, the 46-year-old Costello says, "It was a thrill, of course. I'd met him once at a Swedish folk festival in 1978, and I was rather hoping he didn't remember, because it was at the height of the Attractions' 'young and drunk' period. He did, but in a more comical way than I did."

It may surprise more than Von Otter that Costello and his Attractions possessed a devotion to ABBA songs in their spikiest new-wave days. "We were fanatical about ABBA at a time when they weren't fashionable in England among rock'n'roll people," he says with a smile. "They were pop -- it was like comparing Radiohead to Britney Spears, as you remember. Yet we would go around saying, 'No, these are great pop songs.'"

For her part, the 45-year-old Von Otter -- who grew up mostly in England as the daughter of a diplomat -- admits that before she and Costello became friends, she had no real knowledge of his own esteemed catalog of pop songs.

"It would have been nice if I had some of the recordings and known a little bit more about what Elvis was about," she admits. "But I've caught up a little bit at least... I really admire Elvis' professionalism. He has a huge, long experience of this business in all its facets and uses it with great intelligence." And, she adds with a laugh, that's "nice for me, because I can sit back and let him do all the work, basically."

Although Von Otter's ongoing schedule of operatic, concert, and recital engagements and recordings precludes the chance of many public performances on behalf of "For the Stars" in the coming months, she and Costello did give a showcase performance for about 100 media representatives Feb. 25 at Vienna's Hofburg Palace.

"For the Stars" received a substantial boost in the U.K. on the eve of its release, with the screening of an edition of the long-running arts program "The South Bank Show" devoted to the collaboration. Stateside, a Costello/Von Otter appearance on "The Late Show With David Letterman" is scheduled for June 5.

"Listeners will, I think, take this record to their hearts," Costello says of the album, knowing that the shock of the new will be something to overcome for some. "People can get nervous before they've ever heard a note. But when once you hear it, there's really nothing to fear."

Assistance in preparing this story was provided by Bradley Bambarger in New York.