The midday sun from the atrium skylight of Children's National Medical Center illuminates her rose-petal cheeks. She sits on a folding chair, one hand firmly clasping her violin and the other brushing her long taffeta skirt. She turns and smiles at her mother, glances coyly at her classmates, and then waves briefly at the doctors who saved her right leg.

It's time for Liya Dovgalyuk's solo in this special mini-concert and she plays the Bach Concerto in A Minor crisply, barely taking her eyes off the music. The front row is filled with young patients, some smaller than she was three years ago when the doctors found a rare bone cancer in her knee. As she plays, Liya seems to be holding her breath. Around her the hospital staff watches and silently roots for her, joyous at the sight of their former patient, once shrunken, now bubbling.

When Liya finishes, she gets two sustained standing ovations. She bathes the crowd with a victorious grin, but the conductor has to prompt her to take a bow. Her elementary school classmates surround her, giggling at first, then asking to tour "4 Yellow," the oncology unit.

It was an extraordinary morning for Liya, who's now almost 12. And, in a way, for Children's too, as one of its patients came back to entertain. Yet in another sense the day wasn't unusual for Children's, where the performing arts are often present to ease loneliness. The hospital often resembles an arts festival -- musicians in the atrium, jugglers in the waiting areas, actors as fairy tale characters strolling the floors, and an occasional bedside serenade. Such programs are organized by New Horizons, a national model for programs like these that has been run by Children's since 1978. New Horizons brings together such partners as the Levine School of Music, where Liya studies. She joined a Levine School ensemble, under guest conductor Michael Morgan, for this special performance.

Barely four years ago Liya had a much different life in the middle of a civil war in Latvia; just three years ago, she was an ailing newcomer to the United States, struggling to learn English so she could express her feelings and ask about her future.

For 1 1/2 years at Children's, Liya underwent chemotherapy, had six inches of bone removed and a prosthesis inserted. Eighteen months after the first operation, her other knee required surgery because it wasn't growing properly. Slowly Liya learned to walk again and to bend her knee enough to ride a bike, and now a complete recovery is a strong possibility.

A radiant, squirming fifth-grader, Liya is in her school orchestra and the handbell choir at her church, and studies at Levine with a member of the National Symphony Orchestra. Music has helped her through a lot of hardships.

It was in Latvia that she became enchanted with the violin. "I don't remember, but my mom says my brothers were playing, so I wanted to," she says, casting her huge hazel eyes in her mother's direction. Music was a safe pastime in a dangerous place -- as the Soviet Union teetered near collapse, the Soviet army sent tanks and troops to Latvia to enforce quiet. Liya's grandfather had been a foe of the Soviet government, imprisoned in Siberia for 12 years. This last show of Russian strength, and the uncertain nature of daily life in the Latvian capital of Riga, were too much for Liya's family.

In the winter of 1991, they left. "We thought about our children's futures -- tanks were moving around our house," says Lyuba Dovgalyuk, the strong doyenne of the family. Liya is the youngest of her four children, and the only girl.

Then: "Three months after we came, I felt my knee hurt. The doctor discovered I had a bump," Liya says evenly. "It didn't hurt a lot. It felt like a hammer on my knee, sometime." The doctors found Ewing's sarcoma, a bone cancer with a 70 percent chance of recovery. The family's new life was shattered.

"In the beginning I didn't know what was happening. I was confused because I didn't speak much English," Liya says. It was worse for her mother -- she knew what was happening, or thought she did, based on her experience in Latvian hospitals where she had been a volunteer. "First she amputates," Lyuba thought, "then she dies."

But now here's Liya, restless during an interview at her music school, decked out in a Warner Bros. T-shirt, checking her Mickey Mouse watch, crumpling a soda can in her hand. Her mother swiftly reaches out and sets the can upright on the table, in the silent gesture mothers learn everywhere.

At first, Liya's only spontaneous English was "thank you," and she could scarcely understand what was going on as doctors began chemotherapy in March 1992 and operated on her four months later. The night before that first surgery, all she wanted was to be able to tell the doctor how hungry she was.

Even harder than the treatment was the recovery. "The doctor said he would let me go home when I could pick up my leg," says Liya. To suggest how much work that took, the girl slides her chair back, pushes up her black shorts and raises the leg in question.

"There," she says, looking solemnly at the marks from the operation -- 42 stitches, leaving a thick track from knee to thigh.

During her long hospital stays Liya lost weight, skin color and her nut-brown hair. She was often silent -- not only because of her limited English, perhaps, but also because she had learned to endure difficulties without complaint. "She faced her treatment with grace," says Stacy Nicholson, a physician on the oncology ward.

Music became one of her escapes.

Robert Wyatt, a pianist, associate dean at the Levine school and a volunteer at Children's, saw Liya often but rarely got her to talk. "She usually looked sad and lonely," says Wyatt. "But she perked up one day when a harpist came to the cancer floor. When the woman finished playing the harp, Liya did some strumming. And she brightened."

The family's luck began to brighten. As Liya grew stronger, her mother was able to find work as a cashier at a grocery. One day there was a sale on cauliflower, limit four to a customer. One customer in particular didn't like the limit, and he began complaining in a mixture of Russian and English. Lyuba Dovgalyuk stepped in to mediate. She found herself talking to Lev Pekarsky, a violinist with the NSO.

Pekarsky liked the cashier, and when he heard that she had a family of musicians, he helped steer them to teachers. Pekarsky's son, Pavel, another NSO violinist, now teaches Liya and her brother Eugene, 14. Paul, 15, studies cello at the Levine School while Tim, 17, studies clarinet with another NSO teacher. Her mom is a pianist; only her dad, Mikhail, an engineer, doesn't play an instrument. Lev Pekarsky has since died; his son says Liya is a natural. "What I find unusual with her is you can sit down and explain stuff. She will follow. With most people you have to beat your head against the wall a little bit," he says.

Last summer Liya was well enough to return to Latvia to visit Asya, her maternal grandmother. She, her family and 47 members of the McLean Baptist Church -- sponsor of the Dovgalyuk family -- made the trip with the help of the Make-a-Wish Foundation. The musical family performed at Riga's famous Dome Cathedral and visited the hospital where Lyuba once worked. There, Liya handed out balloons and stuffed animals and told everyone how good the doctors are in the United States.

She's happy to have her brown hair back, and pleased to have gained some weight. The worst of her trauma appears to be behind her. Liya has a full schedule at Spring Hill Elementary School in McLean, where her favorite subject is math. Her English vocabulary is burgeoning -- "television," she explains. She reads, and practices her violin two hours a day.

Music, she says, helped and comforted her when she needed it, and she hopes it can do the same for others. "I guess I like the sound," she says. Smiling and showing a perfect dimple on her chin one recent morning, she says thank you to her friends at Children's, through Bach. CAPTION: Young violinist Liya Dovgalyuk returns for a performance at Children's Hospital, where she was treated three years ago for a rare form of bone cancer. CAPTION: Robert Wyatt, a volunteer who worked with Liya Dovgalyuk at Children's Hospital, congratulates the young violinist after her performance there. CAPTION: Amid cancer and war, young Liya Dovgalyuk has clung to her music. (Photo ran in an earlier edition)