Andrew Lloyd Webber and Stephen Sondheim, the lord and the god of contemporary musical theatre, reside on different planets of composition, but they happen to share the same birthday (March 22). They also share, less ironically, the same Trilby. Her name, next to unknown in this country at this particular point in time, is Maria Friedman.

Their devotion to her is well deserved. Friedman earned an Olivier Award for her Fosca — the doomed, love-consumed Italian romantic in Sondheim's Passion — and is widely regarded as his London muse because of the Sondheim shows and recordings she has done there. This month she changes her tune to latter-day Lord Lloyd Webber and re-creates for Broadway her acclaimed West End portrayal of Marian Halcombe in The Woman in White, a Victorian lass menaced by a corpulent Italian count named Fosco.

Friedman is all too giddily aware of the Fosca/Fosco connection, if only because the bad count is being played here by Michael Ball, who was her Giorgio — the object of her obsessive Passion — and who slipped into Michael Crawford's fat suit when the latter was stricken with "a nonspecific virus" shortly after The Woman in White opened in London. She reports that Crawford is much improved "and has just started working again" — albeit not in the show (Simon Callow is currently playing Fosco to Ruthie Henshall's Marian).

Regardless of which Michael was at the controls, the Swiss-born Brit soprano could always count on the count for a colorful dust-up. "Count Fosco," she cheerfully contends, "is one of the most marvelous, playful villains I've ever encountered. He's a fraudulent, womanizing, hedonistic, food-loving, sex-loving, indulgent human being. In short, he's the person you'd want at every party. If you're going to have a party full of stodgy people, the count would have everyone roaring with laughter in minutes. He'd be a great bridge player, too. He's irreverent and passionate and funny and clever — very, very clever."

Not that her Marian has been short-changed in the clever department, she's quick to add. "Marian's a match for Fosco, and in that period there were very few people who — just because of class and gender — would be able to challenge somebody, head to head, as she does. She has got such courage, putting herself in great physical danger to uncover the dark secret of this story. I tend to think of her as the first female detective in literature. "I just remember thinking how modern she was," says Friedman, who first came across the character when, as a schoolgirl of 13 or 14, she read Wilkie Collins's classic Gothic novel. "It's one of my favorite books of all time — a complete page-turner. I could not put the book down. It's one of the things that converted me into wanting to read a lot."

She even saw the Warner Brothers' film fumble, with Sydney Greenstreet as Fosco and Alexis Smith as Marian. "I didn't use it for research. It's just something in the recesses of my memory."

It has taken a quarter century of conspicuous performing for Friedman to become a critical darling and have someone actually tailor-make a show for her. "I've known Andrew for years — decades! When I was about 22, I met him, and he has played quite a lot with my voice, getting me into a studio to record his stuff to see what the shape of the song is, how it fits into a show. He has often used me for a lot of the demos that he does."

But The Woman in White is the first time he has actually sculpted her into a show, with the assistance of lyricist David Zippel, book writer Charlotte Jones and director Trevor Nunn. "They wrote it around me — with my range, my voice, my acting skills, my sense of humor, my sense of tragedy. They wrote it knowing that I was going to play the lead.

The way Andrew writes, he often will build a song through the evening. You get a little snatch of it here, you get a little snatch of it there — and then you sing a whole lot of it later. Consequently, you're constantly making friends with your songs as you go along."

Yes, she says, there'll be some changes made from the London production. "The thing that's exciting about working with a new piece — and particularly with this team — is that they're not afraid to experiment. Bits they felt could be improved upon, they're rewriting. We can always put them back if they don't work. And we've got a good rehearsal period to try new things. Knowing this team, they'll work every day, right up to opening night."

Which pretty much goes with the territory of a new show. "It can be fun, or it can be torturous. It really depends on the mix. The fact that I'm here, in New York, is testament to how much fun I had in London, because nothing could drag me into doing a show that I don't like doing. Not the money. Not the fame. Not the allure of Broadway. Nothing."

It pleases her she's making her Broadway bow in a role no one else has ever played. "I have to say, 'new' excites me more than anything else. I like new roles. With all that comes with it, I like creating roles. I like that process of not knowing what you're in. A complete blank page. It doesn't always work. It's much, much riskier, but I would rather take the risk. After all, how can I expect to originate a role in New York when I'm a Londoner? It'll go to a New Yorker, so now that I'm here, hopefully the doors will open."

Let the record show: Maria Friedman has arrived — a major player, in a major way.