It would be far more sensible to say "one of the most beautiful" or "the most beautiful I've ever heard," but let it stand at this: Alessandra Marc has the most beautiful voice in the world. Qualifiers -- that it is a big and unwieldy voice that seems to possess her rather than the other way around -- would only detract from a truth that ought to be expressed as extravagantly as the voice it's applied to.

Beginning tonight, Marc sings the title role in Puccini's "Turandot" with the Washington Opera at the Kennedy Center Opera House. Although she lives in Fairfax County, with her husband and daughter, graduated from high school and attended college here and even sang with the Washington Opera years ago as a chorister, she is effectively making her debut with the company this weekend.

Marc was not the original choice to be the star soprano of the sold-out run of "Turandots"; that honor went to Sharon Sweet, who pulled out for health reasons. So the privilege of anchoring the title role for five of the nine performances is, if not exactly an afterthought, a fortunate accident for a singer whose career has been particularly buffeted by the vicissitudes of luck, personality and prejudice.

When Marc first appeared with the Washington Opera in the early '80s, she was an aspiring young singer in her twenties (she doesn't give her exact age); her name was Judith Borden, which sounded too close for comfort to Judith Blegen, another opera singer. So she changed it, cobbling an Italianate first name to a German-sounding surname; her career, which includes a lot of Turandots and some stunning forays into Strauss, is a similar hybrid.

"It just feels right now," she says before an evening rehearsal. "I've grown into an Alessandra."

Marc's voice stands apart from the contemporary opera world, where singers strive for a sensible, tidy sound, a solid technique, a wide repertoire and a long career. Her voice belongs on an old 78, emerging like a distant and eerie light through a haze of pops, scratches and other aural sediment. It is a voice from the past, singing with too much character, too much distinctive sadness, to fit easily into today's businesslike opera world. Which probably explains why her career has not been bigger than it is, yet also why she occasionally crops up in an article like this one, with that impossible superlative attached to her: the most beautiful voice in the world.

Almost 13 years ago, Marc was in Santa Fe preparing to make her U.S. stage debut in a major role. There was an afternoon rehearsal of Richard Strauss's "Friedenstag," an almost unknown work from the late 1930s with a magnificent, almost superhuman role for its lead soprano. The opera ends with an homage to Beethoven's "Fidelio," a long, ecstatic chorus of praise celebrating peace and reconciliation, over which the soprano must sing at a drastically high pitch and volume.

When Marc unleashed her voice that afternoon, the effect on the company was electrifying. The theater slowly filled with costume makers and set painters, idle choristers, box office types, front-office personnel, all drawn to and mesmerized by her sumptuous sound, the sighing, anguished, almost drooping tone, and the magnificence of her high notes -- effortless and transcendent under the brilliant desert sun. Week after week that summer, Marc scored standing ovations and prompted presumptuous chatter among the opera classes that she was definitely going to have a spectacular career.

"That was definitely a turning point," she says. "It was the U.S. premiere of the opera, and that got a lot of attention. There was real excitement."

A year later, an article in Vogue gave her the label: "Alessandra Marc has the most beautiful voice in the world." Andrew Porter, the venerable former critic of the New Yorker and a discriminating judge of voices, was only slightly more circumspect: "Perhaps the richest, fullest, most beautiful big soprano voice around," he wrote.

By some standards she's already had a spectacular career. The role of Turandot has brought her, recently, to New York's Metropolitan Opera, and later this year it will mark her debut at Milan's La Scala. She's made some very fine and prestigious recordings: the title role of "Elektra" for Giuseppe Sinopoli in 1995; the soprano part of Zemlinsky's Lyrische Symphonie with Riccardo Chailly and the Royal Concertgebouw in 1993; Anita in Krenek's jazz opera "Jonny spielt auf," also in 1993. All were made for major labels, all of them with important conductors.

She has sung with enough of the major orchestras to have an impressive if not complete re{acute}sume{acute}, and ditto the major opera houses. But she hasn't been exactly the sort of professional supernova that the woman with the most beautiful voice in the world might have been. The Washington Opera, for instance, has bypassed her for two decades, and in between her first Aidas at the Met in 1989 and her return earlier this season, 12 years elapsed.

Opera is political, and opera houses have strange priorities. Marc is upfront about the obstacles she's faced.

"I haven't always had the best management -- you never know whether you're being sold the right way, or being sold at all," she says. Marc has changed management three times now, which in the close-knit opera world can look restless, impatient or fickle. At the same time, her career has had spikes and troughs -- big European orchestral engagements followed by much smaller opera engagements in this country -- suggesting that she hasn't had consistent and persistent support from her managers.

"And there's a prejudice against 'big' people," she says. Two things are indisputable: Marc is big, in the grand tradition of large women with large voices, and she's quite beautiful. But opera audiences today are more and more obsessed with the visual picture, and the prevalent image of beauty is skewed to the young and thin. Marc says she has lost work as a result.

"I think that opera is about the music, that music should be first," she says. She mentions a prominent European company that is casting a Turandot solely based on the director's notion of physical appearance. "They're looking for a soprano who looks like a 12-year-old girl. I wish them luck."

The prejudice against size, like most prejudices, operates with little logic or consistency. Luciano Pavarotti continues to play heroic and youthful roles, despite his obesity. And other sopranos have been given a pass, despite not quite looking the part.

"Why is it an issue for some people and not others?" asks Brian Kellow, an editor at Opera News who compares Marc's voice favorably with those of Jane Eaglen and Deborah Voigt, two of the most visible practitioners of the dramatic soprano repertoire. "To me she is a much more expressive singer than Jane Eaglen is, and Jane Eaglen is of comparable dimensions physically. But Eaglen's size obviously isn't an issue for the people who are presenting her in all these Wagner operas."

For centuries no one has really required opera singers to look the part. Salome, according to the libretto, is an adolescent girl; onstage she's rarely svelte, or younger than 30.

"Opera has tried to go Hollywood," says Marc. "I think there are a number of reasons. The producer, not the conductor, is making the casting decisions. Photogenic, telegenic, is in. I think the audience that we've lost in the last 15 years [to AIDS] has really hurt the appreciation of good singing."

If the standard of physical beauty onstage has gravitated away from the Rubenesque and toward the alabaster blandness of Herb Ritts, the voice, alas, seems to be following suit. The pressures on singers today are cruel and relentless, and the notion of a pretty voice may well be undergoing a slow, evolutionary adaptation.

"I think American singers, in particular, are trying to do too many things with their voices," says Marc, citing the obligation to sing in multiple languages and in repertoire that is often unsuitable to the particular character of their voices.

Singers, and critics, are not unaware of the problem; it's become a commonplace in opera reviews to lament the loss of grain in the voice -- or as some fanatics put it, squillo: the particular ring that gives the voice edge and character.

Marc's voice is remarkable for having great character without the particular focus and sharpness that sounds harsh to ears used to a more folklike or popular sound. American singers tend to train their instruments until they purr like a Mercedes, and then try desperately to graft onto them something that sounds individual and human. The results often sound bland or mannered.

Marc's voice has escaped the great leveling of modern operatic training, perhaps because her training happened outside the mainstream of conservatories and music schools. Although she enrolled at the University of Maryland and studied voice there, she eventually dropped out and took private lessons from Marilyn Cotlow, whom she credits not only for her insight into the voice but also for her force of personality. Her teachers at Maryland were telling her that someday she might sing lyric roles; Cotlow recognized in her that rarest of female voices, the proper dramatic soprano.

"When she heard that they were telling me maybe someday I'd sing Mimi [in Puccini's 'La Boheme'] she just howled," remembers Marc. Cotlow's training took Marc to the point of getting management in New York, and her first crack at major auditions.

The voice, however, had its oddities. Truth in advertising: Some find the sfumato of Marc's singing -- the blurry roundedness and slightly swooping quality of her attacks -- insufferable, but they're just resisting its charms. Others lament the habit of approaching top notes with a little step-up, a slight throwing of the voice into the upper register; but they're nitpicking. These are the imperfections that give the voice its idiosyncratic beauty.

Distinctive and powerful voices are incomparable in that they establish a world of their own. When Marc sings, her sound is instantly recognizable for its inherent vulnerability. When she talks about her career, and her life, she seems all too vulnerable as well. She talks about being disappointed that she doesn't get more offers to sing onstage; she very much wants to sing Isolde someday. Perhaps she says a bit too much about certain misunderstandings with powerful people in the business; she's honest, which in the guarded, burnished world of opera publicity means she may be indiscreet.

Marc lost 90 pounds in the past year, but then there was Christmas, with its temptations. She shows pictures of her daughter with the undisguised joy of a sailor sighting land after stormy seas.

The things that are difficult or impossible for other singers -- the production of volume and the ease of the top notes -- present no difficulties when Marc is in good voice; the tragic weakness of the voice is in its very size, the sense that it is difficult to be agile, to move from top to bottom, to take corners at high speeds. Marc admits that her voice has changed over the years and that she's had to work on certain bad habits. At the same time, she seems immensely content, in an almost mystical way, with the sound that comes out of her mouth.

"It makes me happy," she says. "To stand up there and really let it out -- it makes me feel connected to God."

Soprano Alessandra Marc has the most beautiful voice in the world. Period.Alessandra Marc will debut at La Scala later this year as Turandot, a role she's also performed in New York at the Met.The singer at home in Fairfax County with daughter Olivia Brakel, 7.