Productions at the Muny almost always start with a flashy number, one that shows off the large, colorfully costumed chorus and the outdoor theater's big sound.

But not Monday night. In this week's opening number, a slender young woman makes her solitary way down a green mountain path to the stage. "The hills are alive," Ashley Brown sings - and at that moment, so is her audience.

Many people love "The Sound of Music," Rodgers and Hammerstein's fact-based musical about the singing von Trapp family. Undeterred by threatening weather, more than 8,900 theatergoers turned out to see it Monday - the biggest Muny opening all season.

And in fact, a little rain did fall. That delayed the start of the production by about five minutes - and gave the first big hand of the night to the stagehands, wielding outsize mops.

"The Sound of Music" makes an easy target. Rodgers and Hammerstein's last collaboration, the 1959 musical wasn't on par with their great earlier work, musically or in its storytelling. The characters in "South Pacific" wrestle with prejudice; the troubled young couple in "Carousel" struggles to find its way at the bottom of the social ladder. Those shows deal with complicated people facing tough situations. But in "The Sound of Music," the bad guys are Nazis; the good guys are nuns and cute motherless children. Commercials can offer more nuance.

But its black-and-white world view may help explain why "The Sound of Music" is so popular. It's like a fairy tale - maybe more like a fairy tale than Disney's "Beauty and the Beast," this season's children's show.

"The Sound of Music" offers the pleasures of knowing whom to like and knowing what will come next. In the hands of director Marc Bruni, music director Ben Whitely and choreographer Liza Gennaro, it also offers the satisfactions of solid musical theater.

As Maria, the young postulant who comes to the von Trapp family as a governess but, through love, joins it as wife and mother, Brown is spirited and down to earth, and her voice is bell-like.

A Broadway star (she was New York's original "Mary Poppins") who got her start in the Muny chorus, Brown commands that opening scene, when she takes the big stage alone. But she isn't alone there for long. The large, well-cast company gives her plenty of good company.

Tom Hewitt plays Captain von Trapp with dignity and just enough hints of warmth to justify the relationship that blossoms between him and Maria. (It's less clear why he sometimes holds a guitar, since he doesn't seem to play it.) There's more good work from Linda Mugleston as the wise mother abbess who sees that Maria's destiny lies outside the convent, Justin Scott Brown as a messenger with a crush on the eldest von Trapp daughter, Leslie Fenniston as a Viennese sophisticate and Lewis J. Stadlen as an impresario who imagines he can make his peace with the Nazis.

Jessica Grové, Christian Probst, Berklea Going, Matthew Howard, Julia Schweitzer, Elizabeth Teeter and Maria Knasel make an appealing line-up as the children; Gennaro choreographs them in simple, effective style.

There are a couple of glitches. When Maria first arrives at the von Trapp's palatial home in the Tryol, the captain and the children remark on her odd dress. But there's nothing especially odd about her brown suit. Later, however, after she has been back to the convent, she returns in a clownish magenta frock with a matching hat. An opening night mix-up? If it wasn't, it should have been - she's dressed wrong both times.

Odder still is Bruni's choice to have a few of the characters speak with German accents. All the characters who use accents are pro-Nazi bad guys, but some of the Nazi sympathizers sound American, like the good characters. Aren't they all supposed to be speaking German anyhow? It's a puzzle, out of place in a show that delights in its deliberate simplicity.