WHAT COULD WELL BE a new concept in musical theater got of to a somewhat shaky start, technically anyway, Friday in Walnut Creek.

Diablo Light Opera Company's Bay Area premiere of the charming musical, "big," may have launched the era of the suburban musical -- a show that plays much more appealingly to regional theater audiences than it did to its original Broadway crowd, simply because the story speaks more pointedly to the land of long commutes and minivans than it does to the dazzling trend-of-the-minute urbanites.

Wait, don't let your with-it Weejuns get all scuffed up here -- the idea isn't designed to put the slam on anyone -- it's simply an observation that in this demographically julienned world, theatrical producers are going to have to find material that appeals highly to very specific groups. And, while a musical about the pains of growing up, the sentimentality of family love, and the gentle charm of children discovering a wider world may not exactly play as cutting edge on Broadway, it certainly performs a symphony on the heartstrings of those of us out here, living lives where somebody's growing up plays a big part.

The keen-eyed, or long memoried will recall there were, years ago, plenty of musicals like this, and, so, if it makes you feel better, call "big" the '90s version of "Bye, Bye Birdie," at least in terms of youthful exuberance and family appeal. But when that stuff played big on Broadway, it was years of "Phantoms" and "Rents" and "Jeykell's" ago.

So what does it all mean. First off, it means the authors of "big" were absolutely brilliant to rewrite their Broadway script, and to continue to hone it as productions moved out into regional theaters around the country. It means Diablo Light Opera Company was very smart to latch onto the rights of this musical version of Tom Hanks' movie comedy as soon as they became available.

The script, still in need of some shaping, is a delight and contains some wonderful songs that move the story well and, at the same time, serve as emotionally evocative tunes in their own right.

But, what 'big' offers that is especially appealing to this area is a chance for a lot of adolescents to perform -- unlike shows such as "Annie" and "Oliver," which rely so heavily on smaller children, 'big' has parts for slightly older kids. And, wow, what a wonderfully talented (and trained) group of youngsters we have around here.

The show starts with a dance routine performed in the New Jersey neighborhood where Josh Baskin (Marshall Johnson as the boy and Patrick Michael Dukeman as the man) lives. These are mostly junior high kids, but they perform like seasoned troupers, and make you immediately fall in love with the show.

As a musical, 'big" pretty much follows the plot of the film. Josh visits a carnival, makes a wish to become big at a fortune-telling machine, and the next morning, he wakes up man-sized, a 12-year-old in a man's body. With no place else to go, he is escorted to New York City by his best pal, Billy Kopecki (an enormously talented Mark Mendelson), where he is quickly hired as a toy expert by the MacMillan Toy Company. Within moments, it seems, Josh wins the wrath of the executive men and the love of a hard-driving female executive, Susan Lawrence (Jennifer Moore).

Meanwhile, Josh's parents are frantic, believing their son has been the victim of foul play. It takes about 21/2 hours to get to happily ever after -- maybe -- but the journey is a fun, bumpy ride through puberty, big business, young love and all the rest of growing up in a matter of moments.

Dukeman is particularly strong in the role of Josh the man, since he has the challenging task of looking like a man but performing, both physically and emotionally, as a boy. He was equally believable in his scenes with Mendelson as in those with Moore, a real tribute to his characterization. Moore, too, was excellent, coupling an extraordinary singing voice with an acting capability that allowed her to play Susan tough as nails and vulnerable at the same time. Joel Fleisher was a delight as the owner of the toy company and Susan Amacker gave the small role of Miss Watson some wonderfully memorable comic touches.

But it was rough on opening night. Technical problems with lights, sets and electronics made some scene changes awkward and at times crippled the pace of the show. This offered another strong argument for companies staging large productions at the Lesher Center to give themselves more preview time in the theater before their official opening date.

The script, too, needs a bit more polish. It falls occasionally to modern musical sensibilities and plays on the dark side, something that just doesn't' work with "big" -- really, the show is a fantasy, a little boy puts a quarter into a machine and turns into a man -- that's fantasy.

Still there is enough to this show to make it an exciting new addition to the musical comedy cannon. It's got the story, its got the songs, it's got the dances, and in the case of the DLOC production, it has the talent to make it a charming piece of theater.