Call it AIDS Aid. Artist Jody Mussoff, who exhibits with Gallery K and who knows quite a few area artists, came up with a simple idea to raise funds for the AIDS program at Washington's Whitman-Walker Clinic. Mussoff asked Gallery K director Komei Wachi if he would donate his space for a one-day art sale benefiting the clinic. After Wachi approved the idea, Mussoff made a few calls, sent out a few letters and posted a few handbills. The response was enormous.

At least 120 artists have volunteered to donate works for the sale next Sunday at Gallery K, 2032 P St. NW. Mussoff has set a flat price of $100 for each piece. Artists who have donated include Manon Cleary, Georgia Deal, Fred Folsom, Tom Green, Rebecca Kamen, Polly Kraft, Jo Rango, Alan Weatherley and Kenneth Young. With so many artists selling at a preset price, there may be a number of good buys. The sale lasts from noon to 6 p.m. Call 223-6955 for information. Mixed Disciplines

Cross Currents -- District Curators Inc.'s creative season of interdisciplinary performances -- continues today with more of the vocal compositions of John Cage, performed by Cage and assisted by Marilyn Boyd De Reggi and the InterArts Ensemble at the Embassy of France on Reservoir Road. But that's barely the beginning of what promises to be one of more original series in the nation's capital this season.

"All of our performances have to do with a mix of disciplines . . . a fruitful intermixing of things," says Susan Resnick, District Curators' special events coordinator.

That is evident from the group's collection of 1985-86 artists, who will perform at the National Theatre, the Kennedy Center, the Martin Luther King Memorial Library and other places around town. Later this month, for instance, a group of Washingtonians -- soprano Annette Poulard, tenor/baritone Jimmy McPhail and tap dancer Johne' Forge's (of Cafe' Lautrec fame) will join the Jazz Workshop orchestra and the D.C. Contemporary Dance Theater in a performance of Duke Ellington's sacred music.

Events scheduled for next year include an Impossible Theatre-produced movie with accompanying computer music, Meredith Monk's multimedia work "Quarry" and a new multimedia work by choreographer Wendy Woodson and director Achim Nowak.

"It's an opportunity for Washington artists to participate and perform with artists from New York and Baltimore . . . and other places," says Resnick, who has assembled the season with cooperation from a slew of arts groups and supporters, including the American National Theater, the Washington Project for the Arts, the Embassy of France, the King library, the Smithsonian Resident Associates Program and the Mayor's Committee to Promote Washington. Three of the season's eight Washington premieres are free. For a complete schedule and ticket information, call 783-0360. Art and History Seminar

The Hirshhorn Museum is offering a free seminar, "Currents," for high school juniors only Dec. 14. It will examine the relationship between art and current historical developments. Participating students' comments and observations will be incorporated into a free pamphlet the museum will distribute to visitors. Applications are due by Friday. Call 357-3235 to receive an application by mail or 357-2700 for more information . . . Two benefits are scheduled for the to-be-displaced Dance Place. The first is a screening of "White Nights" at 7 p.m. Friday at the Circle Avalon, 5612 Connecticut Ave. NW; tickets are $10 and are available at Dance Place, 2424 18th St. NW (462-1321). The other is "The Sampler Dance Performance Benefit," a showcase of 15 dance companies and individuals, at 9 p.m. Dec. 9 at Tracks, First and M streets SE. Tickets are $5 at Dance Place . . . The National Endowment for the Humanities yesterday named Leszek Kolakowski, an international historian of philosophy, religion and Marxism, as its 1986 Jefferson Lecturer in the Humanities. Kolakowski holds academic posts at Oxford University and the University of Chicago . . . The Corcoran, 17th Street and New York Avenue NW, is kicking off its exhibition "In the American West, Photographs by Richard Avedon" with an appearance by the photographer at a book-signing party from 3 to 5 p.m. Thursday. Call 638-3211 for details.