Prelude to a ballet, Scene 1:

On a warm October afternoon, 22 teen-agers in an upstairs rehearsal room stand in rows of five before Mary Day, founder of the Washington Ballet.

"Balance', releve'," Day commands the dancers. Each row comes forward, performs the dance steps and returns to the back of the mirrored room: an army of dancers in multicolored leotards.

The young dancers -- some have traveled from Korea, Hong Kong and Britain as well as Baltimore to study at Day's Washington School of Ballet -- are auditioning for "The Nutcracker," the one ballet each year that gives them a crack at the limelight. In the rehearsal class, she gives an unusual command: Dancers are to run along the diagonal of the rectangular rehearsal space in a loping, S-shaped curve.

"It's hard to say what I look for -- everyone here knows the dance steps, but there's a certain handling of the feet, how the body is carried, a special deportment," Day says as the dancers swirl by. " 'The Nutcracker' is unique because it requires so many children. When they develop, they go on to the next part -- like the Flower Corps or Snow Corps. Many of the girls here used to be Claras," she notes, speaking of the ballet's heroine.

Day says she knows that some of the young dancers won't make it professionally, but she finds a spot for most of them in "The Nutcracker." "They have to feel they've had a chance to try it out on their own."

Day stops the class and dismisses it. "I don't know what we're doing from now on -- just watch the bulletin board," she tells the departing students.

Scene 2:

In a basement rehearsal room two flights down in the white building at Porter and Wisconsin, another group of girls who look about 15 and have been dancing since age 8 are trying hard to look like a corps of snowflakes. As ballet instructor Robert Steele counts out the steps, slats of autumn light from the high windows shift and focus on the dancers' legs, capturing the dance movements like the flickering images of a Chaplin movie.

"Move the legs way down in the pas de chat," says Steele, referring to the elongated position the Snow Corps will take on stage, beckoning to their Snow Queen. For now the Snow Queen, a role given to members of the professional company, is little more than an abstraction as the group practices an arabesque. The dance set ends and Steele walks to another class, where the Flower Corps (as in "Waltz of the Flowers") is gathering. Some of the faces are familiar. The students often double up and dance alternate roles on different nights.

"The Snow Corps is a bit harder to rehearse because more precision is required," says Steele as he flips on a tape of the familiar Tchaikovsky music. A former dancer in the Washington company, Steele played one of the boys in the Christmas party scene early in his career and eventually got to be Snow Prince. This is the first year he and Pat Berrend, another instructor and dancer who played the Snow Queen, are putting the children and young teen-agers in the cast through all their paces.

Outside, it's twilight and 16-year-old Christine Raitt is waiting for a ride home with another ballet student. "We always look forward to 'The Nutcracker,' " she says. "By the time it's over our instructor might say, 'I don't even want to hear the music,' but for us, it's our one time to perform." Twelve-year-old Katie Belmont, a Toy Soldier, puts it differently: "It's fun to put on makeup and act like a ham."

At the ballet:

Backstage at Lisner Auditorium is full of vignettes: the cast of mice who don their furry costumes in the bowels of the orchestra, the Toy Soldiers with their pancake makeup applied assembly-line fashion three flights up, the Mother Gigogne (Mother Ginger) character whose billowing purple skirt requires clearing an entire room to be put on.

Mary Day grabs a little boy about to go on in the party scene; his floppy pants still need pinning. "Go on without him," she tells the other children, who are looking back puzzled. The clock on stage strikes 12 and in the wings Day and a dresser swiftly pull a nightgown over Clara's party dress. They hand her the electric candlelight prop that she'll use to discover the mice eating crumbs at midnight.

No one seems nervous about being under the eyes of the director; the cast members -- more than 250 adults and children, about 150 of whom act in any one performance -- seem alternately excited or relaxed, but not too tense.

"I know I have what it takes to be in the arts," says Miriam Noble, only 19 behind the makeup for the elderly grandmother in the party scene. Noble has been doing "The Nutcracker" for six years. "I decided to take the year off and concentrate on ballet this year -- the morning ballet class at 9:30 and another at 2. I'm not sure if classical ballet is what I want to do, but at age 65, I don't want to think, 'What if?' "

Noble cuts her thoughts short, hearing her cue to head for the stage. "I look forward to this ballet every year," she says. "It's not that I associate 'The Nutcracker' with Christmas, it's just that this time of year means 'The Nutcracker.' "