Sarah Shivers and her friends spent yesterday outside in the cold and gray, rehearsing for last night's tree-lighting ceremony on the Ellipse. They kept warm by doing the Tush Push.

As country music sensation LeAnn Rimes and the U.S. Army Band ran through several renditions of "Put a Little Holiday in Your Heart," Shivers taught her pals the line dance.

"Heel-toe, heel-step, heel-toe, heel-step.

Push it front, push it back, grind, griiind."

The griiind is too much for the teenage girls, and they dissolve into giggles.

One of the onstage organizers winks down at them. "Would you guys like to be in the show?"

The response is a bit of adolescent bravado: "We're already in the show, bub."

Members of the Roanoke College Children's Choir, Shivers and her fellow Tush Pushers came to Washington Wednesday to perform in the Pageant of Peace that accompanies the annual lighting of the National Christmas Tree.

Shivers is a senior at Roanoke Catholic High School, where, presumably, she did not learn the Tush Push. She says she picked up the dance from the Nashville Network. "It's been around for a few years, but I guess it's kind of catching on with teens and stuff."

They spent part of Wednesday rehearsing a medley of jazzy Christmas songs with Patti LaBelle. "It's interesting to hear Patti LaBelle because she's older than we are, and so her voice is different," says Shivers, 17. "Our young voices, we sing a much different style than her."

Different styles is part of what ostensibly makes the pageant, which is presented by the National Park Service, appeal to all Americans, even those who don't celebrate Christmas. This year's entertainment is typically diverse: country singer Rimes, R&B star LaBelle, and the new age noodlings of Mannheim Steamroller.

Even the Christmas tree is meant to be inclusive.

Kathy Presciano, a lighting specialist for General Electric who designed this year's tree, explains that its thousands of multicolored lights "represent the cultural diversity of our nation."

The entertainment also includes the high art of ballet, though it is, of course, the most commercial ballet, "The Nutcracker." After finishing her song, Rimes practices her introduction -- "Now, how many of you children out there have seen a Christmas production of The Nutcracker?' " -- while three teenage dancers behind her shiver gracefully. Even in street clothes, they look the part: neat ponytails and buns, perfect posture, toes in first position.

"Is the tape ready for the ballet?"

The music starts, Tchaikovsky so tinny it is barely recognizable, and Vanessa Matthews begins the exaggerated stiff movements of "The Nutcracker's" wind-up toy. The music stops. Matthews scowls. "My hands are freezing," she says.

The music starts again, less tinny this time, and Lauren Jewell and Lauren Profitt begin their brief duet. They're not actually dancing, just marking the steps -- it's too cold and they already know them by heart.

The girls are members of the Washington Ballet's pre-professional Young Dancers troupe. Recently they've been performing in area hospitals, dancing the "Mini-Nuts," a half-hour excerpt from "The Nutcracker." For last night's brief program, they danced excerpts from the excerpts.

The dancers are not the least bit distracted when two conspicuously oversized M&Ms -- one red, one green -- are led to the area in front of the stage.

LaBelle's entrance is far more dramatic. She's wrapped in a full-length hooded black coat and black sunglasses. Her heels are so high she needs help getting up and down the stairs leading to the stage.

Her makeup is fabulous. Her nails are fabulous. She looks only slightly less fabulous when her sunglasses come off so she can read the prompt cards held up before her.

She may as well have left them on. "It's Christmas," she warbles. "I don't really know what I'm singing, but that's all right."

After the first run-through, LaBelle explains her improvising. "I just couldn't see. It's so cold I can't see," she says. "Oooh, child, it's going to be cold tonight."

She wipes her eyes with some tissues.

Behind LaBelle, Shivers and her 63 choirmates stand nervously in neat rows. Shivers has taken her wool hat off. She'll wear it later, but not for the rehearsal. It's itchy, she says, and far worse -- "It's kind of goofy."

After LaBelle's rehearsal, TV reporters swarm around the star as she teeters back to her limousine. They ask her about the cold, her voice and the true meaning of Christmas. She signs a few autographs.

The departure of Shivers and her choirmates from the stage isn't nearly as grand. There's a tent nearby where they can warm up, but soon they must clear out so that the Army Band can have a turn. Shivers is tired -- they've been up since 5 a.m. for an appearance on the "Today" show -- and there's a second round of rehearsals in the afternoon.

She picks at the turkey on a croissant in her box lunch. "We expected to be out here all day, so we're just trying to adapt," she says brightly. "I'm trying not to let the cold get my spirits down." CAPTION: Warming up: Patti LaBelle rehearses yesterday afternoon for the National Christmas Tree lighting festivities. CAPTION: Lauren Jewell, a member of the Washington Ballet's Young Dancers troupe, rehearses her part of "The Nutcracker" for the tree-lighting ceremony on the Ellipse.