LONDON - Though the clock hadn't yet struck noon, soprano Ailyn Pérez was dressed for the evening and pouring herself champagne.

The sip didn't go down well: Suddenly, the next note in her La Traviata rehearsal was lost in the bubbles of what was really sparkling cider. So the cider was ordered bubble-free next time - in her official debut this week at one of the world's great opera houses.

Philadelphia has seen the Chicago-born Pérez rise from a promising Academy of Vocal Arts student to one of today's singers-most-likely-to-succeed. And now, at age 32, that's what she's doing, in what is considered the Hamlet of soprano roles. After last week's dress rehearsal, she faced the London critics Monday in a house that has seen such late legends as Maria Callas and the artist to whom Pérez is often compared, Victoria de los Angeles.

Intimidated, she's not.

"They're my heroes. Maybe they used to haunt me," she says, "but they're my courage too."

The living like her, too: Most reviews so far have been excellent. Graham Rogers from called her "youthful and radiant" and had only minor reservations about her coloratura technique. In the London Times, Hilary Finch gave the Traviata revival 41/2 stars out of five, calling her voice "supple and strong enough to sustain long passages in the most eloquent and perfectly controlled half voice." In past London performances, Pérez has been described as "entrancing."

Backstage at the Royal Opera, Pérez is already a hit. In the company's 2010 tour of Japan, she "covered" for Traviata star Ermonela Jaho, who fell ill after Act I on opening night. Most of the difficult music is in Act I, so Pérez relaxed into the rest of the role, which she says practically sings itself. The often-reserved Japanese rewarded her with a roar, but what she most remembers was what happened minutes later.

"When the curtain came down, the chorus congratulated me backstage. That was another roar. I'll never forget it," she says. "And these are the people I was with for three weeks in Japan. Some of us went to see Mount Fuji together. I feel part of the family."

Now at the opera company's home in Covent Garden, Pérez was delighted to see that the company is using its older Traviata production, originated by director Richard Eyre and immortalized in a recording and video that made Angela Gheorghiu a star in the 1980s. Pérez even wears the star's elegant black dress, and if it ever goes missing, she'll be the likely suspect.

"It's gorgeous. Drop-dead gorgeous. I didn't realize I'd be wearing it until I came in for a fitting. I first saw that black dress on the album cover with Gheorghiu. I thought, 'My God! I'm on top of the world.' "

With a cast that includes British baritone Simon Keenlyside as Germont and Polish tenor Piotr Beczala as Alfredo, she feels, more than anything, a sense of freedom: "There's nothing better than being next to a great singer. You can fully sing out. You don't have to worry about them."

Though Pérez has plenty of credits in the great opera capitals of Europe, they haven't always offered a platform as solid as this one. Casts of standard-repertoire revivals are often a revolving door; it's not unusual to meet your costars for the first time during the performance. Making matters even more complicated are modern productions with idiosyncratic viewpoints.

At Pérez's 2009 Traviata at the Berlin State Opera, Violetta bore an intentional resemblance to Marilyn Monroe and was onstage the entire opera. The idea was that the opera was Violetta's life passing before her eyes, which meant that in several long scenes, Pérez was directed to lie collapsed on the floor. In one concession to creature comforts (and vocal freshness), two drinking straws stuck up through the stage floor.

"The first night I couldn't find the straws. Second night, I found the straws but I had fainted in a way that I couldn't reach over to them without breaking character," she says. "Third night, I thought, 'What is this really doing for me? And do I really want to drink that water?' "

No secret straws are needed for her sustained hydration at the Royal Opera House; the London Traviata is blessedly traditional.

After last week's rehearsal, as Pérez emerged from the stage door into the damp London afternoon, colleagues smiled and nodded to her, and she almost swept past her husband, tenor Stephen Costello, nearly unrecognizable in a homeboy hat turned sideways.

He was a little peeved: "She's in her own world!"

"But we were talking about Maria Callas!" she firmly explained.

Costello, who is recovering from food poisoning, will go into the London Traviata in January, though in a different cast, without his wife. "It's Netrebko," he says of his Violetta - Anna Netrebko, with whom he opened the Metropolitan Opera season in Anna Bolena. Pérez's parents will visit at Christmas to see her last performance; Costello's family is back home in Northeast Philadelphia.

Walking through the London streets, extravagantly decorated for Christmas, they passed the cozy West End theaters, many built a generation before the oldest ones on Broadway, and in a configuration that stage actors love because the balconies seem to hug them. The Royal Opera balcony is too far from the stage to administer hugs. But the acoustic, Pérez has found, does much the same thing.

"Finally I've had a chance to let my voice go through the theater. It feels so good to sing here, the hall warms everything," she said. "Anything you do that's subtle and dramatic is going to read."

At times, her Violetta was so transparent you felt you could read Pérez's mind. In Act III, when she has left the love of her life to preserve his social standing but is rudely confronted by him at a party, Pérez seemed so fragile, you feared she might break like a twig. Is it possible that the illness that kills Violetta in Act IV is already full-blown in Act III?

Pérez is puzzled by that thought. Illness is not what she is thinking: "You know what it is? She can't keep it up anymore. She can't be beautiful anymore. She can't be Violetta. She's done."

And what a luxury it is to project such fine shades of detail in a medium representing opera at its grandest, in a house that is among Europe's most glamorous.

Contact music critic David Patrick Stearns at