SAN FRANCISCO (CBS SF/AP) – For Patricia Racette, this was already shaping up as a memorable year at the San Francisco Opera, opening the season in Boito’s “Mefistofele” and returning in June to headline two more productions.

Then, suddenly, along came “Dolores Claiborne.”

Less than a month ago, the American soprano agreed to take on an almost unheard-of challenge – rescuing the world-premiere production of Tobias Picker’s opera based on the Stephen King novel. Mezzo-soprano Dolora Zajick, for whom it was written, withdrew at the last minute, and David Gockley, the company’s director, appealed to Racette to step in.

“I took as thorough a look at the score as I could, and it’s fiendishly difficult,” Racette said in a telephone interview this week. “But I’m a quick study, and I thought, gosh, it’ll be to the wire, but I think I can do this if I just pull one of my turbo-sessions.”

Her partner, mezzo-soprano Beth Clayton, bought a 4-foot electronic keyboard for their apartment, and they used that to help her learn the role.

“I’m not exaggerating at all to say that every waking hour has been spent preparing,” Racette said. “The only breaks I’ve had are my performances of `Mefistofele.'”

Why subject herself to the pressure? It’s not as if Racette were a fledgling artist, hungry for a breakthrough. She’s an established star, who at 48 regularly performs at the Metropolitan Opera and other leading houses.

“I do relish the challenge,” she acknowledged. “And San Francisco is my artistic home. I have incredible loyalty to the company and to David. And almost immeasurable affection for the public here.”

Though born and raised in New England, she served her apprenticeship in the Merola Opera Program in San Francisco, debuting with the company as the Priestess in Verdi’s “Aida” in 1989. She’s returned almost every year since.

In addition, she said she was drawn to the title character, a hard-bitten housekeeper in rural Maine who was memorably portrayed by Kathy Bates in the movie version. “This rather salty, sort of sour character,” as Racette calls her, “is certainly a departure from the typical repertoire that I play.”

And there’s more: Picker and his librettist, J.D. McClatchy, also collaborated on an earlier opera, “Emmeline,” which first brought Racette to prominence when she originated the title role in Santa Fe in 1996. (She also sang in another Picker opera, “An American Tragedy,” at its Met premiere in 2005.)

So she’s now appearing in four operas during the company’s current season – fully half the lineup of eight works. And they’re coming in the form of double-headers: “Dolores Claiborne” runs simultaneously with “Mefistofele,” and in June she’ll alternate a signature role, Puccini’s “Madame Butterfly,” with the part of Julie in the classic American musical “Show Boat.”

“The joke now is I’ll only come here if I can sing two roles at once,” she said.

But what happened to Racette just before the dress rehearsal for “Dolores” was no joke.

“I actually had the gall to be human and have a horrible allergy attack,” she said. Ordered to rest her vocal cords, she went through Sunday’s dress rehearsal acting the entire role but just mouthing the words while her understudy sang the part.

She recovered well enough to go on for Wednesday’s opening, and the initial reviews were positive for the soprano, if less so for the opera itself.

Now is she looking forward to a long break when her current stint is over in early October? Not exactly. Racette said she’ll have “a couple of days to get back home (to Santa Fe, N.M.), switch my suitcases” and head for New York, where she starts rehearsing Puccini’s “Tosca” at the Met. Later in the season she’ll take on a new role with that company, the part of Maddalena in Giordano’s “Andrea Chenier.”

More new roles are coming soon: Minnie in Puccini’s “La Fanciulla del West,” Marie Antoinette in John Corigliano’s “The Ghosts of Versailles” and the title role in Richard Strauss’ “Salome,” which she will debut next summer in a concert performance at the Ravinia Festival outside Chicago.

Salome, who demands and gets the head of John the Baptist on a silver platter, requires a singer who can be heard over Strauss’ thick orchestration. Though Racette is a lyric, rather than a heavier-voiced dramatic soprano, she is optimistic she can meet the challenge.

“For a lyric soprano, my voice likes soaring high and then singing low, and Salome frequently sings in the lower portion of her voice and then shoots to the top,” she said. “She has a lot of bite to her vocally and as a character, and that is a good match for me.”

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