THEATER : Break a Leg, Mr. Hyde : Just when you thought that musical extravaganzas were starting to be washed up, pop musicians are creating a whole new batch. The latest gig: that old tale of two personalities.

‘Jekyll & Hyde,” an ambitious new musical opening its national tour at the Orange County Performing Arts Center on Tuesday, is helping to bring back an old Tin Pan Alley tradition: putting pop in the theater.

The show’s producers are betting millions on doing what “The Who’s Tommy” did for rock opera and “Smokey Joe’s Cafe” did for Lieber and Stoller’s golden oldies: capitalize on the appeal of popular composers.

It’s a high-risk venture designed to revive an ailing theater industry badly in need of new musicals that speak the language of the young.

“If you remember,” says “Jekyll & Hyde” composer Frank Wildhorn, “Gershwin and Porter and Rodgers and Hammerstein were the popular songwriters of their day. Their route was the theater. The shows gave rise to the songs. The music industry promoted their songs to sheet music. And the songs became calling cards for their shows.”

Today’s exemplar, of course, is Andrew Lloyd Webber. His tunes have become pop standards and have built an audience for his musicals as nobody else’s have. Gregory Boyd, the director of “Jekyll & Hyde,” likes to quote what he calls “the best thing Lloyd Webber or anybody ever said” on the subject: “I don’t want people coming out of the theater humming the songs. I want them going in humming the songs.”

Wildhorn, 36, who is also creative director of Atlantic Theater, a new label being developed by Atlantic Records, wrote Whitney Houston’s mega-hit “Where Do Broken Hearts Go?” and roughly 150 tunes sung by artists as varied as Kenny Rogers, Jeffrey Osborne, Peabo Bryson, Liza Minnelli, Sammy Davis Jr. and the Moody Blues.

Remarkably, his “Jekyll & Hyde” has already spawned two albums under two record labels before getting to Broadway.

“The Romantic Highlights from ‘Jekyll & Hyde’ ” was released in 1990 by RCA before the show had a production at all, a rare event twice achieved by Lloyd Webber and Tim Rice with “Jesus Christ Superstar” and “Evita.” And last January, when “Jekyll & Hyde” had a $3.5-million pre-touring production at Houston’s Theatre Under the Stars, Atlantic put out a double CD, “Jekyll & Hyde--The Gothic Musical Thriller.”

The RCA album is reported to have sold 100,000 copies. Meanwhile, Atlantic “has done very well,” according to its president, Val Azzoli, who said that 32,000 albums have sold domestically--25,000 in Houston alone--and that in Australia the album has hit the charts at No. 18.

“I look at ‘Jekyll & Hyde’ like a rock show,” Azzoli said by telephone from New York. “When a rock record goes out and there’s a tour, we basically follow the tour. We did that with Michael Crawford’s record ‘EFX.’ He was on the road for almost a year playing two weeks in every town. We sold 750,000 albums. That opened my eyes.

“Radio is not out there to play this type of music, not like it used to be. So the vehicle is touring. When the show is playing a town for a week or two, we just inundate the market. We do television, morning programs, afternoon programs. We do in-store signings. We saturate that market totally. That town is our universe.”

If all goes as planned, the producers of “Jekyll & Hyde” (Pace Theatrical Group and Fox Theatricals) expect it to reach Broadway in the spring of 1996. By then it will have toured to 37 cities, including Dallas (where it just had a two-week preview), Sacramento, Atlanta, New Orleans, Miami, St. Louis, Chicago, Denver, Cleveland and Baltimore.

Presumably, the show will sell many more albums. And if it succeeds in New York, a third recording--the Broadway cast album--will be next on Wildhorn’s agenda.

When Wildhorn sits down at the piano in his Woodland Hills living room to play a couple of his recent theater tunes, the native New Yorker looks suddenly transformed from a voluble song-plugger into an intense and private artist.

His eyes close. His powerful torso--he’s built like a young Yogi Berra--sways gently. Everything he has been talking about nonstop for the past two hours drops away: his formative years at USC; writing his first musical in 1979; dropping out of school and getting his first songwriting contract in 1983 from Sam Trust, who ran ATV Music, which owned, among other things, the Beatles catalogue.

What emerges under the spell of Wildhorn’s melodic touch are “Living in the Shadows,” the 11 o’clock number he has just written for Julie Andrews in the Broadway-bound musical “Victor/Victoria” and “A New Life,” one of several power-pop ballads for Linda Eder in “Jekyll & Hyde.”

He is not the only popular composer shifting his attention to the theater. Paul Simon has been laboring for years on a musical called “Capeman.” In 1993 he teamed with Derek Walcott, the Nobel Prize-winning poet, to write the book and lyrics.

“They’re going into a workshop in the next few months,” Simon’s assistant, Vaughn Hazell, said from New York. “Paul has demo tapes prepared, and he’s almost done.”

“Capeman”--the title could change--is expected to open in Chicago in November, 1996, before heading to Broadway.

Meanwhile, Randy Newman’s new musical, “Faust,” will premiere Sept. 24 at the La Jolla Playhouse.

Reprise Records plans to release a studio album of the songs from “Faust” just before previews begin. Although nobody from the La Jolla cast is on the recording, the Reprise release will have an all-star lineup--James Taylor, Don Henley, Linda Ronstadt, Bonnie Raitt, Elton John and Newman--guaranteed to focus attention on the show.

“There is no shortage of people writing musicals,” says Jim Thessing, executive director of the National Alliance of Musical Theaters. “About 60 new musicals premiere every year across the country. Usually we see them starting out in the regional theaters. But most of them will play one production and probably never be heard from again.”

By that measure, too, “Jekyll & Hyde” is unusual--despite its sometimes frustrating production history.

Wildhorn conceived the show more than a decade ago at USC with a college friend, Steve Cuden, who wrote the lyrics. They loosely based the story on Robert Louis Stevenson’s Gothic novella, “The Strange Case of Dr. Jekyll & Mr. Hyde” and any number of movie versions.

In 1987 Wildhorn gave a cassette tape of their songs to the British-born, two-time Oscar-winner Leslie Bricusse, who is perhaps best known as the lyricist for his 1960s musicals with Anthony Newley (“Stop the World--I Want to Get Off” and “The Smell of the Greasepaint--The Roar of the Crowd”) and for a string of pop hits (“What Kind of Fool Am I?,” “Who Can I Turn To?,” “Goldfinger” and “Talk to the Animals”).

“I was on my way to Mexico at the time and didn’t listen to Frank’s tape until two or three days later,” Bricusse recalls from Chicago, where he was preparing “Victor/Victoria” for its fall Broadway opening.

“When I put the tape on, I realized within moments that it was very special musically. I thought it had enormous potential. Lyrically, it was nothing at all.”

Wildhorn and Cuden went their separate ways. Bricusse stepped in and rewrote the book, giving Wildhorn the chance to compose fresh music for new “Jekyll & Hyde” songs. In their first couple of sessions, they created “This Is the Moment” (to become the unofficial anthem of the 1992 and ’94 Winter Olympics), “Once Upon a Dream” and “A New Life”--all still in the show.

Some early reports have claimed that “Jekyll & Hyde” has a bombastic musical signature not unlike Lloyd Webber’s “The Phantom of the Opera.” Bricusse strongly disagrees.

“I think stylistically Frank and Andrew are very different,” says the 64-year-old, Cambridge-educated lyricist. “I know Andrew well and I know Frank well. The music of those two men is very much like the men themselves.

“With Andrew’s music it is very easy to see what his background was. His father ran the Royal College of Music in London. Andrew has a very musically educated style, with great awareness of classical material. Therefore, his music is more studied.

“Frank has a much more natural, passionate talent. His gift of melody is quite remarkable. I have written, I guess, over a hundred songs with him now. When you’re doing a song with him, he gives you choices. You don’t get just one.”

It wasn’t until 1990, after a New York producer picked up the rights and then couldn’t raise the money to get the show on, that “Jekyll & Hyde” received its first production, at the Alley Theatre in Houston. Again, it was a tape of the score that provided the way in.

“Frank sent me a demo [of the RCA album],” Gregory Boyd, the Alley’s artistic director, recounts from Dallas. “At that time people were sending me all kinds of horror stories because we had done ‘Frankenstein’ and ‘Dracula,’ things like that. I said, ‘Oh God, not another one.’ But then I heard the songs and said, ‘What the hell is this? And who is that girl who’s singing?’ ”

She was Linda Eder, a 12-time “Star Search” winner who had swept the $100,000 grand prize, met Wildhorn and bowled him over in an audition for “Jekyll & Hyde.” He fell in love with her voice (and with her--they now live together) and began tailoring songs for her, including “Someone Like You.” (RCA and Angel did her two solo albums, and Atlantic has just signed her.)

The Alley mounted a $500,000-production starring Chuck Wagner in the title role and Eder as a prostitute involved with both Jekyll and Hyde. The show was to run four weeks. It ran nine and would have kept on running, Boyd says, if Wagner (later to star as the Beast in “Beauty and the Beast”) and others in the cast hadn’t had previous commitments.

“ ‘Jekyll & Hyde’ was an amazing thing,” the director recalls. “People were scalping tickets in the lobby for $500 a pair. In a lot of ways it was the most successful show the Alley ever had--in terms of the box-office gross, in terms of people fainting, in terms of people trying to sneak in.”

After another unsuccessful attempt to get the show on Broadway--this time with a $300,000 New York workshop that turned into “a complete disaster,” Wildhorn says--the creative team returned to Texas and approached Frank Young, who heads Theatre Under the Stars in Houston and the Fifth Avenue Theatre in Seattle.

Working with a combined budget of roughly $25 million a year, he is the nation’s largest nonprofit producer of new musicals.

With Boyd directing again, the Alley and Young co-produced a fully developed “Jekyll & Hyde” at a cost of $3.5 million. It opened last January with Robert Cuccioli at Theatre Under the Stars and ran for 4 1/2 weeks, followed by three weeks in Seattle.

“We made all our money back and then some,” Young says. “The show grossed $4 million.” In Houston, moreover, it grossed more than the opening four weeks of “Beauty and the Beast,” which Young also produced in its 1993 pre-Broadway tryout.

“For ‘Jekyll & Hyde,’ we had people coming back four and five times,” he explains. “I met one woman in the lobby who said she had tickets to all 35 performances. People began coming in costume. It was like ‘The Rocky Horror Show.’ ”

The producers of the tour essentially picked up that production, keeping Cuccioli in the title role and Linda Eder as his co-star. They added new scenery and costumes and invested an additional $1.8 million to put it on the road.

“I work with a lot of pop writers who are much more successful than I’ve been,” Wildhorn says. “And they say to me, ‘Why do you want to do that?’ Don’t forget, there is no money up front in the theater. No matter who you are, it’s almost always on spec. To write a Broadway score for the Dramatists Guild minimum, we can have dinner. Unless you’re a Paul Simon or a Billy Joel, you can’t afford to take time away from the recording career.

“I was very fortunate to work with some wonderful writers a few generations older than me. I saw that as a lot of them approached their late 40s and 50s, they no longer had an interest in what was on the radio. But they were prisoners of their own success. They had to keep writing pop to support their lifestyles. And yet creatively it was not healthy for them.”

Bricusse is convinced that Wildhorn is “so passionate about the theater” that he is on the verge of switching careers.

“As soon as a major success in the theater comes Frank’s way, which it will, whether it’s this show or the next one,” he says, “I suspect you won’t see much of him on the pop scene anymore, except as he bears out his theory that when the great ones were writing in the ‘30s, more popular songs came from the theater and movies than anywhere else.”

In fact, Bricusse is doing his best to keep Wildhorn in the theater. After the death of Henry Mancini, who was working on the score for “Victor/Victoria,” Bricusse says, “two or three very celebrated composers who were friends of Hank’s and mine quietly offered anonymous help. I asked Blake [Edwards] for Frank. He’s a great student of the theater--and he’s fast.”

And he’s prolific.

In addition to composing “Jekyll & Hyde” and adding songs to “Victor/Victoria,” Wildhorn has two other musicals ready to go: “The Scarlet Pimpernel,” which producer Pierre Cossette recently signed for a Broadway production, and “Svengali,” which the composer and Boyd hope to get on soon.

That doesn’t include Wildhorn’s job of writing scores for Warner Bros. animated musicals, the pop ballet he has nearly finished and the pop opera he has been commissioned to write for the 50th anniversary season of the Alley Theatre, where he’s an associate artist along with Robert Wilson and Edward Albee.

Wildhorn adjusts the baseball cap on his head.

“Look,” he says, “more than anything else I’ve learned from doing all of this is that it’s OK to wake up tomorrow morning and fail--if you see your vision through. At the end of the day, if you’ve put your heart and soul into these things, that’s what counts.”

* “Jekyll & Hyde” plays Tuesday through Sunday at the Orange County Performing Arts Center, 600 Town Center Drive, Costa Mesa. Performances are Tuesday-Saturday, 8 p.m.; Sunday, 7:30 p.m.; matinees Saturday and Sunday, 2 p.m. $19-$49.50. (714) 556-2787.