THE NATIONAL Folk Festival, the oldest multicultural folk fest in America and a fixture at Wolf Trap since it opened 12 years ago, won't be returning to the rolling meadows of Vienna. Joe Wilson, head of the sponsoring National Council for the Traditional Arts, says, "We were trying to figure out just what the hell we were doing putting on a third folk festival in Washington" (the other two being the Smithsonian's Folklife Festival and the Washington Folk Festival, both of which are free, unlike the National). "So we're going on the road again."

The National Folk Festival started in 1934 and was held in different cities before coming to Wolf Trap in 1971. "No one ever envisioned it staying there that long, it just slipped into the calendar." The new location probably will be Cuyahoga Valley National Recreation Area, the new national park in Ohio.

The NCTA is a private, nonprofit association that fosters traditional folk music, dance and crafts. It emphasizes the carriers of tradition, those people who have sustained America's rich cultural diversity through generations in both family and community settings. The group's principles have been widely adopted at regional and local levels, and the NCTA serves as a voice in Washington for those concerned with traditional arts.

Though the folk festival has moved on, the NCTA continues to work out of its tiny Dupont Circle office with a small-town touring program started in 1978. The touring program "really influenced us to do most of our work outside the Washington area," says Wilson. Kicking off with an Irish tour called the "Green Fields of America," the programs have included "Echoes from the Ozarks," "Der Yiddisher Caravan," "Raices Musicales" (Tex-Mex) and "Teater, Visafton och Bal" (Swedish-American). Funding comes from the Folk Arts panel at the National Endowment for the Arts and from community sponsors.

"There's a concept to the touring," Wilson explains. "We take the best of an art to the people who originated it, rather than necessarily exposing the whole wide world to it. If you're touring cowboys, as I'm going to be doing in May in a program called "The Old Puncher's Reunion" , take them to the cattle towns.

"The second thing is to emphasize quality--people remember that when they've forgotten everything else. The third critical thing is to assemble the best artists you can get from several locations. On the cowboy tour, we've got a cowboy from Hawaii who does a little hula and plays some uke, a Louisiana swamp cowboy who's half-Indian and who wears rubber boots when he herds cattle, an Arizona cowboy . . . we're trying to show the range of the material.

Wilson chooses the members of the touring groups based on his experience with the National Folk Festival, from working with state folklorists and "from being out in the country." His job often is full of discovery: the Appalachian tour included a stop here because "Washington has the most hillbillies in it of any city in the United States; people think it's Detroit or Cleveland--but in the 1970 census, if you take Appalachian counties and figure out where people went . . . they're around this city."

The same holds true for Cambodian refugees, Wilson says, and the NCTA has helped sustain Khmer traditions through the Khmer Classical Dancers (a West Coast tour starts next month). Wilson met many of the dancers and musicians--most of whom now live in the Wheaton area--in Thai refugee camps in 1980. "We helped get them into the country, with a lot of other folks."

All of the touring programs and folk festivals (there are several regional variants put on by the NCTA) are recorded and made available to public radio free of charge. "An incredible amount of it has been broadcast nationally," says Wilson.

Wilson and his small crew ("there's so few of us, we can only handle one tour at a time, but we're always in the position of having one in the batter, one being rolled and one in the skillet") soon will head for the West and Southwest. Wilson himself will travel with the cowboys on a tour that kicks off in Kerrville, Tex., and winds through New Mexico, Arizona, Nevado, Utah, Montana and North Dakota. "The cowboys range in age from 37 to 79--one of 'em fought in Vietnam and one of 'em went west in a covered wagon, walked along and drove two milk cows all the way to Oklahoma."