The Butterflies Go Along With Sarah Brightman on Tour : Performing: The star of “The Music of Andrew Lloyd Webber in Concert” considers concertizing riskier than playing a character in a musical.

At a top-secret location in San Francisco, Sarah Brightman was being held hostage to fame last week. She could not reveal where she was. Nor could her publicist, who said separately from New York that Brightman was under strict orders from her husband, Andrew Lloyd Webber, not to disclose her whereabouts.

But in a voice that sounded bell-like even through the telephone line, the singer did allow that she was “very much cocooned” or “very much marooned”--the words were less clear than the voice--in an ordinary hotel room with blue walls and blue and white curtains. “I’ve got a bathroom,” she added. “There’s a piano and an exercise bicycle.”

Although her road accommodations seemed a bit of a comedown from her usual igs--the nine-room duplex she shares with her husband in Manhattan’s Trump Tower; their 1,350-acre estate in Hampshire, England; their seaside villa on the French Riviera; their Belgravia flat in London--Brightman could rest assured that she was safely ensconced at an unbreachable distance from the kooks and the cranks.

Yet she felt unsettled. For all her well-arranged seclusion, the inevitable butterflies had found her--attracted no doubt by the high expectations she has for her current national tour of “The Music of Andrew Lloyd Webber in Concert.” The butterflies had found her in Milwaukee, followed her from Chicago to Denver, and at that moment in San Francisco, where she was about to give her first West Coast performance, they were fluttering in her stomach again.

“I’m fine, but I’m nervous,” said Brightman, who is to begin a 12-day engagement Tuesday at the Orange County Performing Arts Center in Costa Mesa. “I’m nervous wherever I open. I’m always nervous. I suppose that’s just part of (performing). They say when you’re not nervous, you should stop.”

The former star of Webber’s “The Phantom of the Opera” said she finds concertizing considerably riskier than playing a character in a visually spectacular musical because the essentials are laid bare. “You can’t hide behind the sets or the costumes,” she said. “In the concert hall, the audience has come for your voice and your personality.”

Brightman, a soprano, is backed on this tour by a 60-piece orchestra and supplemented by a company of singers. She said the idea for the concert originated two years ago with a more modest evening of songs that she and her husband had put together at London’s Barbican Centre. Its success, she said, prompted them to develop a an anthology of 23 tunes from eight of his musicals over two decades.

With songs from the early “Joseph and the Amazing Technicolor Dreamcoat” to the less-well-known “Requiem” and “Song and Dance,” the concert is intended for “people of my generation who haven’t seen all of Andrew’s shows,” said Brightman, who is 29.

The program is also something of a poor man’s “phantom,” with no less than seven selections from that musical. Yet,asked which of her husband’s songs she would take with her to a desert island, Brightman said she wouldn’t choose any “Phantom” tune.

“I did them for so long, I’m not sure I would sit and listen,” she said.

More to her liking, Brightman said, are the title song from “Jesus Christ Superstar” and “Don’t Cry for Me, Argentina” from “Evita.” Both pop-chart anthems of the ‘70s are included in tonight’s program, along with the suite from “Starlight Express” and three selections from “Cats.”

In the meantime, Brightman’s former allegiance to rock ‘n’ roll has apparently reasserted itself. The singer, who at 18 joined a group called Hot Gossip after deciding she lacked the talent to become a ballet star, said she has just completed recording an as-yet-untitled rock album due out early next year.

That would represent a considerable shift from her recent recordings. In 1988 she made an album of folk songs by Benjamin Britten. Her latest effort, “The Songs That Got Away,” is a collection of 15 tunes that either flopped or were cut from the musicals for which they were written--by such composers as Irving Berlin, Marvin Hamlisch and Leonard Bernstein.

“To tell you the truth, I really wasn’t a huge musical-theater fan as a youngster,” said Brightman, who nonetheless made her stage debut at 13 in a West End production of the Charles Strouse musical “I and Albert.”

Curiously, she landed in the original London production of “Cats” as a dancer, not a singer. It wasn’t until she left for “Nightingale,” another Strouse musical, that her voice got Lloyd Webber’s full attention.

By then, though, the rest of her had gotten his attention as well. The singer and the composer were wed in 1984, after divorcing their previous spouses, and swiftly became the musical theater’s most celebrated couple.

“We’ve been lucky,” Brightman said.

Even so, she can’t help getting butterflies.

“The Music of Andrew Lloyd Webber in Concert” will open Tuesday and run through Nov. 18. at the Orange County Performing Arts Center, 600 Town Center Drive, Costa Mesa. Curtain this week: Tuesday to Saturday at 8 p.m. Curtain next week: Sunday at 2 p.m.; Monday to Friday at 8 p.m.; Saturday at 2 p.m. Tickets: $19-$40. Information: (714) 556-2787