From behind the foot-high, meter-wide stack of papers on his desk, just opposite the Jordanian oud (lute) lying casually among the guitars, Jonathan Eberhart says, "People will flock to hear a banjo picker, but they'll stay away in droves from a group from Outer Far Offistan." Not this weekend. Eberhart and cosleuth Mia Gardiner have discovered international musicians from 30 countries, Washington-area residents all, who will share their traditional music with 25,000 neighbors.

Each year, with the slogan "Bringing Washington Its Own Music," the Folklore Society of Greater Washington presents its free Washington Folk Festival at Glen Echo Park. And each year Eberhart, a reporter for Science News who once ran a radio program on international folk music for WGTB, and Gardiner, a nurse and musician who initiated the Folklore Society's search for international talents, find the unfound musicians in Washington's varied international communities. "You can walk down the street and count accents," Eberhart says. They have become masters of the hunt.

"It's easy to find a good banjo player," he says, "but how do you find an Eritrean krar lyre player?" If you're Eberhart you hail a cab that runs out of gas, and when the driver turns to apologize in accented English you ask, "Where do you come from?" This opener is always followed by, "Do you play, or do you know someone who plays music from your country?" You battle language barriers, contact your krar player and get invited to a party she's giving "for a few friends" -- 350 of them.

"Musicians are usually known within their community," says Gardiner. "Many who perform at the festival were professional musicians in their own countries who haven't been performing here." Judith and Ingrid Morroy, who have been singing together for 14 years, will present songs in Sranan, the lingua franca of their native Suriname.

"We're having a fantastic family of Vietnamese musicians," Eberhart says, referring to Nguyen Dinh Nghia, who taught at the Saigon Conservatory of Music and makes the instruments his family plays, including the dan bao (single-stringed wooden instrument) played by his daughter. "I've never heard sounds like that come out of a dan bao."

Sometimes the groups they bring from basement gatherings to the concert stage stay there. Ganga, a group of Indian musicians who gathered weekly to play for their own pleasure, now performs regularly. Rumin ahui, an Ecuadorean group of dancers and musicians, began the same way, as did Kyoko Okamoto, a koto player brought back by popular demand year after year.

Filling the 30 slots allotted to international performance takes a lot of questing and questioning. "I have never had the equivalent of anybody slamming a door in my face," says Gardiner, who was once jokingly challenged to find a Chinese opera. (She did.) Embassies, not usually contacted because "they only know the ones already known," occasionally supply helpful leads. One led to singer Kristinn Sigmundsson, who with Asdis Crosby will perform Iceland's traditional unaccompanied songs, characterized by harmony in parallel fifths.

"I feel it's important to represent the new immigrant groups," Gardiner says, noting this year's representation by Laos, Vietnam, Afghanistan and Ethiopia. "For next year, Nicaragua and El Salvador are high on my list."

The musical sharing results in a unique experience, Eberhart says, with the audience and the performers "doing something together. We're all raising sails on the same ship. That's not just what makes it fun. It's why it's a good thing." In the next breath he mentions an 11-foot-long Swiss alpenhorn -- "so you can talk to your neighbors in the next Alp" -- to be played by Richard Spicer, a National Park Service geologist. "You don't have to go through a travel agent to hear this stuff. It's all around here," he says. "That should blow you away!"

The festival runs on volunteer energy, 8,000 hours of it, donated by more than 500 performers and crafts people and 100-plus volunteer staff. The National Park Service provides three employes and the Glen Echo grounds, which are used to capacity during the two-day event. "You couldn't pay somebody enough money to do this, but it's absolutely worth doing for free," Eberhart says.

The Washington Folk Festival, from noon to 10 p.m. Saturday and noon to 6 p.m. Sunday, features four stages for music and dance performances, a children's area, crafts demonstrations and sales, a storytelling area and continuous participatory dance workshops.