"Marc just totally gets it," Waters says. "I think the score of South Park, the movie, is one of the best scores ever and exactly the kind of humor that you need to work on my movies."

On a rainy Tuesday in late March, Shaiman and his personal and professional partner, Scott Wittman are performing a half-hour Hairspray presentation in the crowded sound studio of their spacious Chelsea apartment. The two dozen guests include the fashion director of Bloomingdale's, the director of major gifts for the YWCA (who'd like to use Hairspray as a fund raiser) and the president of the largest group sales company in the country, Group Sales Box Office, which represents 15,000 groups.

These dog-and-pony shows are usually performed in front of several hundred people who buy blocks of seats for theater parties and groups. Lion chose the more intimate setting because "I thought it would be really fun for people to see where a show was born and see the artists up close."

Today's presentation is Shaiman and Wittman's third for Hairspray, and Shaiman is nervous. Standing in the kitchen before the guests move from the living room into the studio, he notices small half moons of perspiration forming on the underarms of his pink shirt. "I don't know why I'm nervous," he says repeatedly.

It's not that he's shy about performing. He's been doing it for much of his life, including a year on the road at age 17 as vocal arranger for his idol, Bette Midler (who is one of Hairspray's investors). But he's not accustomed to having a roomful of, at times, poker-faced strangers in his home, seated inches from his keyboard. Usually, he says, "applause is how you gauge [reactions] - that or laughs - but the real test of these things is the phone calls that come afterward."

Perched atop the upright piano at one side of the studio is a TV monitor on which the movie plays silently throughout the presentation. Fast-forwarding the video, Shaiman turns up the volume at a few select places, pointing out lines that "stuck out" and were transformed into song titles.

One of these comes after Tracy persuades her mother, Edna, to go on a shopping spree that results in an Edna makeover - from high heels to high hair. "Momma, welcome to the '60s," Tracy exclaims.

Laughter breaks out in the small studio when Shaiman announces that Harvey Fierstein is playing Edna, the role created on film by Waters' late cross-dressing star, Divine. Waters initially suggested Anthony Hopkins, Wittman tells the amused guests, "but once he saw Harvey in the role he fell in love with him."

"Once we knew we had Harvey Fierstein in the role, we added a second verse," Shaiman continues as he launches into Tracy and Edna's duet, "Welcome to the '60s," complete with a gravelly imitation of Fierstein's rumbling baritone.

Shaiman's association with Hairspray dates back almost a decade, even before producer Lion became involved. At the time, the rights belonged to Scott Rudin, a theater and film producer with whom Shaiman had worked on a half dozen movies, including South Park.

Shaiman thought the musical would be an ideal opportunity to collaborate with Wittman. Nearly two decades ago, the pair had created several off-Broadway musicals with such titles as The G-String Murders, Trilogy of Terror and Livin' Dolls, the latter containing what the New York Times described as, "wickedly accurate parodies of early-60's teen-age rock-and-roll."

But Shaiman and Wittman didn't get the chance to work on Hairspray; Rudin let the rights lapse, and Hairspray seemed to have fizzled out. Then in the summer of 1999, Lion called Shaiman. "The key is to try and choose people whose sensibility obviously matches the underlying material," the producer says.

Shaiman and Wittman are convinced they're the right match. "There's a certain irreverence and, obviously, a love for bad taste," says Wittman, 47, the taller, thinner, gray-haired member of the pair.

Not to mention that they have never quite "fit in," in the words of Shaiman, 42, the shorter, sandy-haired, goateed and more animated of the two. "Scott and I have always worked with people who are too rock and roll for theater and too theatrical for rock and roll," he explains.

Even so, Lion was hesitant when Shaiman suggested collaborating on the lyrics with Wittman. A couple for 23 years, Shaiman and Wittman may be the only romantic partners ever to write the score for a Broadway musical. "People who live together also working together can be very, very difficult," Lion says.

Undeterred, Shaiman persuaded her to let them try writing a few songs. By September they had written Tracy and Edna's "Welcome to the '60s"; a girl-group trio, "(Momma) I'm a Big Girl Now"; and a Motown-flavored number, "Big, Blonde & Beautiful." All three are still in the score.

"I thought they were terrific," Lion says.

The first time Lion met with Waters, she offered him the chance to write the musical's libretto, or script. He declined.

"I've never written a Broadway play before. It isn't my expertise," the filmmaker says. He also knew instinctively that the musical had to be different from the movie - otherwise, "Why would you do it? You have to turn it into something else."

And how does he describe that "something else"? "The fat girl meets Ethel Merman," the filmmaker says. "That's what it has to be."