Follies: Ghosts of Dancers Past and Future.

There are ghosts haunting the Belasco Theatre, where Stephen Sondheim's legendary musical Follies has been revived by the Roundabout--and I don't mean the shadowy showgirls in pale, shimmering violet who seem to ooze from the blackness of the backstage setting.

Nor am I talking about David Belasco, who, in one of Broadway's more endearing legends, is said to be still hanging around his old upstairs office.

I'm not even thinking of the ghost of my younger self, the one who saw Follies in 1971 and identified with the young dreamers in the show's flashbacks rather than with their older, sadder incarnations, who seem so much more comprehensible to me now.

No, the ghosts that struck me with such force as I watched the show this time around were in the dancing. Any revival must contend with the specter of the original. But there are originals of originals of originals in this story of a group of follies performers who stage a reunion at the now-decrepit theater where they had all once glittered, only to be joined onstage by their youthful doubles and their dashed hopes.

Follies uses the vocabulary of the Broadway revues of George White and Florenz Ziegfeld, which dominated American musical theater between the two world wars, to make rueful comparisons between youth and maturity, desire and disappointment. And just as the show, which was conceived by Harold Prince, layers the past with the present, choreographers who staged the elaborate numbers of those old revues--Russell Markert, Jack Cole, even Michel Fokine and Balanchine--hover over the pastiches in Follies. Then there's the ghost of Michael Bennett, who choreographed and co-directed the original production. And as if they were not company enough for any choreographer, here come octogenarians Marge Champion and Donald Saddler, to dance the featured adagio.

"It's a little intimidating to know that you're choreographing for a two-time Tony-winning choreographer like Donald Saddler and a living legend like Marge Champion," says Kathleen Marshall, who, when you get right down to it, doesn't sound all that intimidated. "But they were so great--they have that wonderful dancer's discipline that never goes away. They were very respectful, and I considered it a great compliment when after we'd work on something they'd say, `This feels right.'"

If the old pros presented her with one set of worries, there were neophytes to present another. The show's ghostly versions of the young characters are all played by performers with dance training. But most of the older members of the cast--headed by Blythe Danner, Gregory Harrison, Judith Ivey, and Treat Williams--came without the pedigree of Champion and Saddler. "It was a challenge to choreograph for the age ranges and ability ranges in this show," she says. "They're all over the map."

Without knowing what physical skills the non-dancers would be bringing with them, Marshall could not prepare as she usually does. "I had to wait to get in the room with them. So I started out with more unknowns than normal. And it took a while, just because people learn steps at different speeds."

Aware that the actors had roles to master and songs to work on as well, and not wanting to waste their time as she experimented, she came up with a novel solution: "I used the chorus kids to figure out the steps and the spacing and then I brought in the older ones. `Watch your ghosts,' I told them. Sometimes they would get a little frustrated at how much quicker the ghosts were at picking things up. But I said to them, `That's what they do. That's what they're here for. You're here for other reasons.'"

Marshall may have been teaching them the steps, but the show's older women, who include Polly Bergen, Betty Garrett, Jane White and others, were teaching her something as well. "It's a real lesson to see them, at their age, in the shape they're in. These are strong people who have been doing this their whole lives. And it keeps them strong. It keeps them young. They really are inspiring." In one vivid scene, the older women revive a "mirror number" in their party dresses while the ghosts perform the original in their gaudy follies costumes. "That Michael Bennett concept is what that number is about," says Marshall, who never saw the 1971 version but knows that many of Bennett's choreographic ideas are now part of the show's structure. "That's what gives it its meaning. You don't have to juice it with much more. Just the joy of seeing these disparate women all doing these same steps in time says everything you need to say."

On the other hand, she notes that the women are now doing her steps, her choreography. "We're not re-creating anything. I did all my research and had it in my head when I was working. Then I shaped the dances based on who the characters were and what Sondheim's music was telling me to do." And in the ballroom number now done by Champion and Saddler, she effected a complete transformation. The original, Marshall says, was a bolero: "We took the same melody and made it into a slow fox-trot, so that it's more Fred and Ginger and suits Marge and Donald better."

So the show that came to her with some Ziegfeld and some Bennett now has some Marshall. And when it's revived in the future, she will be among the ghosts dancing in the head of the choreographer.

Sylviane Gold has written about theater for the Boston Phoenix, The Wall Street Journal, Newsday, The New York Times and other publications.