NEW YORK -- It's a strangely warm November afternoon in Manhattan, but inside a crowded Midtown rehearsal studio, where the windows are flung open to let in the balmy autumn air, the holiday season is well underway.

Decked in red Santa hats, actors Stephen Bogardus and Michael Gruber flash bright smiles while belting out the lyrics to Irving Berlin's "Happy Holiday." The scene finishes and a gaggle of lithe young dancers surrounds the two leads for a run-through of the jaunty "Let Yourself Go."

The sound of tapping toes, snapping fingers, and sweeping feet fills the room as young women wearing pink tutus and young men in green tap shoes and sweats move about the floor, shimmying, sliding, and leaping. With the number's ebullient end, the room erupts in applause, and director Walter Bobbie and choreographer Randy Skinner smile and nod in approval.

The show they're rehearsing is ''White Christmas," which opens at the Wang Theatre on Friday. Based on the 1954 Bing Crosby holiday classic of the same name, the Irving Berlin musical premiered in San Francisco last year to enthusiastic reviews. Wang Center for the Performing Arts CEO and president Josiah Spaulding Jr. says he was so jazzed about the show when he saw it there that he wanted his own production for Boston.

''It's a big musical. It's got 24 musicians in the pit, 33 actors onstage, big sets, big costumes, and big dance numbers," says Spaulding, who was looking for a holiday show to fill his theater in the years when the ''Radio City Christmas Spectacular" wasn't in town. ''And it had been such a long time since I had seen such a big musical that would fit so well on the Wang Theatre stage -- since the original 'Phantom' and the original 'Saigon' and original 'Beauty and the Beast.' "

Spaulding hopes that the musical, about a couple of Broadway dance men who mount a benefit show to save a ski resort from financial disaster, will be a gift for the Wang Center: a package filled with glittering, MGM-style production numbers; dazzling, Broadway-size scenery; and lots and lots of dancing. There's even a machine that will make real snowflakes fall from the ceiling at the end of every show.

After all, the Wang has a lot riding on ''White Christmas." Spaulding's new business model sees the Wang not just presenting or hosting touring shows, but moving into the producing arena. ''White Christmas" marks the organization's first attempt to mount a large-scale production and is a major investment. Co-owned by the Wang and the Ordway Center for the Performing Arts in St. Paul, Minn., this production, if successful, will shift between the two venues every other season. (In a controversial move, the Wang gave the boot to Boston Ballet's ''Nutcracker" last year in favor of the Radio City Rockettes.) The Wang has invested $3.5 million in upfront costs for ''White Christmas," and the Ordway has added $1.25 million. In turn, the Wang hopes to reap the kind of profits it has not seen in recent years (see sidebar ).

''These are very different times than [we've] been in the last four or five years," Spaulding says. ''And one needs to find new business models to create that excitement going forward."

While the spectacle of ''White Christmas" may draw audiences in, its heart and soul, says Bobbie, is Berlin's indelible music. The prolific composer and lyricist wrote hundreds of songs in his lifetime but only two Broadway shows: ''Annie Get Your Gun" and ''Call Me Madam."

''Here is a great American writer of theater music and film music, and there are no shows!" Bobbie exclaims. ''To me, it seemed a great opportunity to pass on a wealth of music in a context that could actually be replicated and seen by generations of people."

Bobbie, who won a Tony Award for the long-running revival of ''Chicago," has been a Berlin fan for years. ''There's an elegance and a simplicity and an inevitability in [Berlin's] writing that is very hard to match," he says. ''His lyric writing is so genuinely colloquial that you feel like you could have written it yourself. Then when you examine it, [you see] it's blindingly sophisticated. You think, 'I Love a Piano' and 'I'm Happy' -- those are going to be good songs? Yet these things have become standards."

The process of turning ''White Christmas" into a stage musical was not easy, and Bobbie had less than a year to pull it off. The first challenge was that the film contains only a handful of Berlin tunes -- not enough for a full musical score. So the need to add other Berlin songs was inevitable. ''You can't really put that film onstage so much as you can put that story onstage," he says. ''The film begins with a bunch of scenes in a war zone. You can't start a musical that way."

The show's 1950s-era plot is fairly simple. World War II buddies Bob and Phil (played by Bing Crosby and Danny Kaye on screen) go on to become a successful Broadway act. When they meet a pair of showbiz sisters following a gig on ''The Ed Sullivan Show," the four head to a ski resort in Vermont, which is owned by Bob and Phil's former Army boss. Unfortunately, the warm weather has left the resort bereft of snow -- and hotel guests. To help the general save his business from ruin, the guys stage a Broadway-style revue at the resort and invite all their old Army buddies to come on Christmas Eve.

The problem, explains Bobbie, is that the film ''is riddled with incident." So he recruited longtime collaborator David Ives to hone the book and remove distracting minor plot points. ''We had to figure out what was essential to this story and simplify it," he says.

They also had to reconfigure the way the songs were woven into the story. Many of them needed a more theatrical presentation. ''In the film, the four [main characters] just sit around a table on a train and sing the song 'Snow.' " In our show, it became an opportunity to illuminate Bob's resistance to go up to Vermont and it became a big production number," Bobbie says. ''So yes, that song is there, but it's exploited in a completely different way."

Assisting Bobbie are some top-notch Broadway talents, including choreographer Randy Skinner (''42nd Street"), set designer Anna Louizos (''Avenue Q"), and costume designer Carrie Robbins (the original Broadway production of ''Grease").

With three productions of ''White Christmas" up and running this winter -- in San Francisco, Los Angeles, and Boston -- Bobbie says the biggest challenge is to avoid making them carbon copies of one another. ''I've had to figure out how to cast three different productions and to honor the personalities of the stars who have come in to do it," he says. ''All my years in ''Chicago" have helped, because you find a way to exploit [an actor's] natural gifts to inform the same part."

For Bogardus, who plays Bob, performing in an irony-free show about lovable characters is a dramatic change of pace from the darker material of recent parts in ''M. Butterfly" and the well-regarded off-Broadway play ''The Pavilion." ''Walter has said over and over again that he doesn't want any sarcasm or cynicism to creep into these characters," Bogardus says. ''And he's vigilant about that."

As Bogardus and his fellow cast members, including Nashua native Kerry O'Malley, rehearse in New York, the crew in Boston is busy installing sets on the cavernous Wang stage, including the sliding barn doors that serve as the backdrop for the finale.

And all the while, Spaulding has kept a watchful eye over the proceedings. ''White Christmas" is a gamble, but Spaulding says he thinks audiences will come. Of course, he's also hoping the snow machine doesn't go on the fritz.

Recalling the first time he saw the show, Spaulding says, ''The barn doors open and it begins snowing outside. Then the cast turns to the audience, and it starts snowing not only in the barn, but it starts snowing on the stage. Then as you're standing up and cheering, it's not only snowing in the barn and snowing onstage, but it's also now snowing in the entire theater. That just blew me away."