The classic image of America as a melting pot is compounded in Washington, where East meets West, North meets South and distance telescopes to nearness. In fact, if the pot boileth over, it's mostly because of an abundance of ethnic spices over visible here than in any other American city. This weekend, for the fifth straight year, Glen Echo Park hosts the Washington Folk Festival, a celebration of neighbors, the "just folks" who have maintained connections wiht their past traditions even as they anticipate the future.

"I never fail to be staggered by how many people come to the unaccompanied ballad workshop," says Helen Schneyer, a spirited folk revivalist and practicing psychotherapist who will be splitting her time between leading "the God Workshop" (gospel singing), and contributing to work song and ballad workshops. Amlaset Abay, who was a television and recording star in Eritrea before coming to Washington in 1972, will abandon her Northwest restaurant for the weekend to pluck her krar, an east African wood instrument that's a distant cousin to the guitar. There will be bagpipes from Scotland, kotos from Japan and dulcrimers from Applachia; blues and bluegrass, sea chanteys and mountain hollers, and dance steps with Lithuanian, Finnish, Mexican, Cambodian, Chilean and Greek accents.

In fact, Glen Echo will turn the world into a smaller -- but brighter -- place for 48 hours . . . and it's all free.The festival will feature 34 international groups, 28 workshops, 32 mini-concerts, 200 dancers in 16 hours of participatory programs with callers and live music, and an assortment of traditional craftspeople. Altogether, almost 500 local performers will celebrate their art today and tomorrow; another 150 organizers, stage and sound crews and other volunteers from the Folklore Society of Greater Washington, will contribute to making what Abe Brumberg says is "a marvelous way to get a cross-cultural overview of America and the contributions to American culture and worklife" of its multi-faced ethnic population.

Brumberg, a 27-year Washingtonian who will perform Yiddish songs, points out that "singing is a sideline to me," a sentiment echoed by almost all the performers, who will step away from everyday lives to share the diversity of their roots. Brumberg, for instance, is an authority on Soviet-Eastern European affairs, a former editor of the Problems of Communism journal, which may have inspired his album, "My Darling Party Line," a collection of humorous songs and parodies of left-wing movements around the world. Brumberg recorded that album 10 years ago with Joe Glazer, long known as Labor's Troubador, who will be performing his songs of coal miners, textile workers, lumberjackets, steelworkers and railroaders at the festival.

Had he been less interested in traditional Hawaiian and Tahitian music, David Nickerson, who now works for the State Department, might be better known today as an alumnus of the original Kingston Trio; as a high school student in Hawaii, he sang in a trio with Nick Shane and Dave Guard, but those two "were more interested in doing American folk music." Several years later, some of the songs surfaced on the first Kingston Trio album, but Nickerson was already committed to government career. When he contacted WETA folk host mary Cliff about programming Hawaiian music, "she asked me to continue my preaching at the festival. I do perform for family and friends whenever they can stand it, but this is a second childhood," Nickerson laughs.

There are plenty of tenuous government connections among the performers, though the festival is thoroughly apolitical. Many of the ethnic participants are here with embassies or international organizations, or, in the case of participants from Southeast Asia, through social or political motivations. Hita Brata Roy, for 20 years the political analyst at the American Consulate in Calcutta, finally realized his interest in ethnomusicology when he retired and came to Washington in 1978. Roy, who will lead a workshop on the instruments and music of India, is "committed to the music that the common people sing, even here. I've been to Appalachia and to bluegrass festivals. It interests me a lot."

The 25-member Grupo Folklorica Chile was formed six years ago and proved to be its own melting pot by including several Costa Ricans, Cubans and "one American, who happens to be my wife and the number two dancer in the group," according to economist and founder Carlos Mirando. The group's costumes are sent from Chile by Mirando's family. "We try to explain to people how the dances came about, so that they're also learning a bit of history. There's a tremendous thirst about other cultures, and people really want to know what we do."

At Glen Echo this weekend, visitors are encouraged to ask questions, to join in the dancing and the singing, to "get the know your neighbor," as one singer puts it. Much of the music continues year-round in Washington's ethnic restaurants and at concerts, but for two days, its under one convenient tent called (hopefully) the big blue sky. "This whole area is a gold mine," says Helen Schneyer. Dig it.