During the week he is a truck driver and stock clerk, carting bolts of fabric around the city.

But this is Sunday, and he is gliding through a tiny room in the basement of the Cambodian Buddhist Society where boys kneel on brightly colored rugs and coax bell-like music from large wooden xylophones.

Though the National Endowment for the Arts has just designated him one of this country's master musicians, Chum Ngek lives a modest life. Wearing a gold-and-brown shirt, white chinos and gray socks, he walks softly among the youngsters, his gaze intent on their hands. He stops, hearing a soft ringing that he wants to correct. Without a word, the middle-aged man stops behind a student, reaching over his shoulders to grasp and lift his hands and the mallets. After a few minutes of coaching, the notes coming out of the 21 keys of the xylophone click along like precise steps on a smooth walkway, each note quick and definite.

The hands guide student after student. Chum hums as he guides the young hands. The students frown in concentration. For these boys, Chum's hands are a connection to a tradition, the pin peat music of Cambodia, the music meant for royalty and the gods.

Master Chum fled his homeland more than 25 years ago, during the brutal period when Cambodia's Khmer Rouge government killed a quarter of the country's population. But he could not bear to leave his music behind, and he wants his American-born students to understand the sounds that were so much of his boyhood.

He glances back at a student who has struggled today. The boy's progress pleases Chum. He smiles and rubs the student's thick black hair.

Remembering the sounds of his childhood is easy. Teaching can be a challenge. "Their parents want them to learn their culture and traditions. We have the young ones for two or three years. Once they hit high school, they change. So we have new students almost every year," he says. The distractions are the ones facing every teen, from the store logos on the T-shirts to the comic book that appears as soon as Chum moves to another side of the room. "It is harder teaching here than at home. I try to explain that music is an exercise and helps you relax."

Since his arrival in the United States in 1982, he has worked to preserve the music of Cambodia. That means exposing his new countrymen to the ceremonies, dance and music that give younger Cambodian Americans a sense of their musical identity, and even remind the adults of rituals that may now be fading.

For his work, the National Endowment for the Arts is saluting him as an artist of the highest rank in the folklore field, and the only local artist to be honored this year. In September, when the NEA honors practitioners of their heritage, he is slated to receive an award named for folklorist and performer Bess Lomax Hawes.

"Master Chum, to me, is the best Cambodian xylophone player alive and he happens to be here," said Sam-Ang Sam, a Cambodian artist and a past National Heritage Fellow. In addition to the classical pin peat music, Chum also performs and teaches a style that deals more with earthly issues, such as love and geography, called mohori, and ancient wedding melodies, called phleng kar.

When the students disperse, he talks about his work and life along with his daughter, Sovath, 22, a molecular biology and Spanish student at Towson State University, and Joanna Pecore, a doctoral candidate in ethnomusicology at the University of Maryland, who has studied his music.

The Buddhist Society's headquarters, on the upper reaches of New Hampshire Avenue in Silver Spring, bulges with activity after the Sunday morning services. It's one of the hubs for the region's estimated 30,000 Cambodians. The music classes last two or three hours. The air still carries the spicy scents of lunch. Girls in bright-hued costumes are practicing their traditional dances. A group of young girls is playing London Bridge. A robed monk is on his cell phone. There's an animated conversation about a wedding and the Cambodian traditions.

Playing for his own enjoyment and passing on the traditions come naturally to Chum, who picked up his first instrument at 10 in his village of Anglong Vil in western Cambodia. Eventually he would learn about 14 instruments, including the hammered dulcimer, called the khimm; the hand drum, or sampho; the bowed fiddle, or tror; and the gongs, or kong. His grandfather, Heng Um, could play eight instruments from the obo to the high-pitched circular drum, and they played together in an orchestra.

At age 18, Chum was named a master teacher, or krou.

But war tore apart his country, and in 1975, when Chum was in his early twenties, Pol Pot and the Khmer Rouge came into power. That bloody reign ended when the Vietnamese army invaded. "Around 1979 the Vietnamese came and everyone migrated," says his daughter.

Chum left behind most of his family and his instruments. He and his wife, Vorn, went to three different refugee camps, the first on the Thailand border called Kaho-I-Dang.

There they found new families, but also ways to keep the old music.

"I didn't have any instruments with me. I would make the instruments myself in the camp and then would make some to sell to people. The bamboo, I made the instruments from the bamboo, was taken from the houses," he says. Before the war, the xylophone was made from teak or bamboo. He made the treble xylophone, the roneat aik -- the instrument on which he is considered the best.

After a year he was sent to another camp, Galang, in Indonesia, where his daughter was born in 1982. He was recognized as an essential teacher, bringing music to the camp, and accompanying dancers who were also refugees. "I taught music the same as at the other camp," he says. A refugee organization assigned some of the dancers to Wheaton, Md., and Chum followed, mainly to be around people he knew. Pecore, who has taken classes with Chum, fills in one detail: "The group wanted you to come here because of the music. He is being modest. They needed him so they could dance."

In agreement, Chum allows a soft-spoken yes. But he offers another reason for the choice of resettlement. "I waited until my daughter was born," and also for his name to be picked in a lottery, he explains. The family also includes a son, Sovann, 24, and Chum has brought his mother and several of his siblings to the area. He's been back home twice.

In his new life, Chum toured with the dancers to concerts, festivals and weddings. He began to attract some students and his teaching career was reborn. "I started at home, private lessons at first," says Chum, who works as a truck driver, delivery person and stock clerk for a fabric store. By the mid-1990s he was teaching at the local temples. After he finishes his classes in Silver Spring, he teaches again at the Cambodian-American Heritage community center in Arlington.

The music made all the passages from the old to the new, and back to the ancient, tolerable.

"The traditions started with music at the temple, also played for the dancers and then for the royalty in the kingdom," he says. He explains the epic of Reamke, a 2,000-year-old tale about the prince who is tested as he roams the world. "When the action happens in the story, the musicians have to play," he says. The heart of the music is the xylophone, which establishes the tempo and the melody, and leads the rest of the instruments, and the two-faced drum which regulates the beat.

The folk songs celebrate the history of Cambodia, the richness of the land, the beauty of the countryside. Some are tributes to the royal and religious figures. Each performance opens with an offering to former teachers, called Sathukar. "It is a happy song, like an opening and calling the teachers to help," he says.

And being a teacher is important to him. "When I see the students are able to play that instrument it makes me happy," Chum says. In the fall his musicianship will be easier to pass on when he releases a CD of his interpretations of pin peat.

One of the many things that keep him aware of the world he left behind is age. He thinks hard when asked his age. Because of the differences between Cambodia's lunar year calendar and the Western calendar, it's not an easy question. "Here I'm 51, back home I'm already 52."

Chum Ngek teaches Ronal By the xylophone at the Cambodian Shrine and Temple in Silver Spring.Chum Ngek instructs Gunarat Lorn in the finer points of the kong, or circular frame gong.