A musical based on familiar children's stories would seem like the right choice for a summer production, wouldn't it?

But if your idea of fairytale-derived theater is Lisa Matsumoto's blissful local favorite "Once Upon One Time," it's worth pointing out that Stephen Sondheim explores different territory in "Into the Woods."

Sondheim's 1987 Broadway musical won three Tony awards and came late in his career — 30 years after he collaborated on the blockbuster hits "West Side Story" and "Gypsy." Matsumoto's pidgin take on fractured fairy tales followed Sondheim's by four years, premiering at the University of Hawai'i in 1991 to huge audience success and jumpstarting her work as a playwright.

But Diamond Head Theatre's summer show takes a denser, darker and more daunting path from Matsumoto's local favorite. It's questionable whether Sondheim's musical will succeed with young children.

Directed and choreographed by John Rampage, with musical direction by Roslyn Catracchia, the show gets excellent staging but suffers from significant flaws.

It has a sharp, professional look, built on bushels of false hair by makeup designer Jess Aki and richly colored and detailed costumes by Karen Wolfe. Derron Peterson's basic set design shifts easily from cottage to forest with the help of tubelike tree trunks that furl down from the rafters like sea creatures.

Rampage keeps the ensemble cast's excellent singers and actors moving with brisk precision.

But the first major concern is audibility. Perhaps it's several shrill soprano voices, perhaps it's the sound system, and perhaps it's the quick, intricate Sondheim lyrics, but many of the full chorus numbers and several of the women's solos are difficult to understand. When the music hits the upper registers, we strain to understand the words.

The second problem is length. The first hour and a half feels like the longest Act One in the history of musical comedy. It also closes with some confusion — the action seems complete, requiring one of the characters to shout out "to be continued."

On opening night there were several empty seats following intermission, indicating that the occupants believed the show to be over or that they had seen enough. But anybody who left before Act Two missed the best stuff.

While Act One follows familiar characters to their expected happy endings, the second half suggests they should have been careful what they wished for, because getting it doesn't guarantee they'll live happily ever after.

In Act One the characters must risk going into the woods to confront its dangers and win their prizes. Going back to that dark place again in Act Two because of new, greater threats makes it even more forbidding. Some even die there.

Mothers and fathers are absent, distant, or cruel. Children are isolated or estranged. Characters and relationships are filled with flaws. But comic irony keeps things from becoming too black.

Sondheim's lyrics and book dialogue by James Lapine are complex, witty and wry. When Jack is upbraided by his mother for selling the family cow (a charming prop designed by Douglas Scheer that assumes silent character status) too cheaply, we learn that "when the end is good, it justifies the beans." How can you not love that kind of writing?

Characters take unexpected twists. A blade-carrying Little Red Riding Hood trades in her cape for a wolf-hide wrap. The pair of princes, after marrying Rapunzel and Cinderella, develop yens for fresh, equally inaccessible young maidens.

Joseph Morales is winsome as Jack, Scott Moura is the lovable Baker, and Zenia Zambrano Moura neatly maneuvers the character twists taken by the Baker's wife. High school sophomore Nataysha Anne Echevarria shows remarkable talent and poise as Little Red Riding Hood, and Elizabeth Hartnett gives Cinderella a refreshing edge.

There's a lot to see and hear in a "Woods" that, for all its loveliness, can also be dark and deep.