An open window to the past -- "The New Painting: Impressionism 1874-1886" at the National Gallery of Art's West Building CLASSICAL MUSIC

The annual Mozart Festival of free, lunch-hour concerts in the World Bank auditorium will begin at 1 p.m. tomorrow with the Manchester String Quartet and continues through the remainder of the week. trio programs are a major feature of the week. Besides Tuesday's concert at the World Bank, they include the Beaux Arts Trio, Friday night at the Library of Congress, and the Philadelphia Trio, this afternoon at the Phillips Collection.

Beethoven's Violin Concerto and Mozart's 25th Symphony are on the program for the Washington Chamber Orchestra, performing tomorrow night with violinist Timothy Baker in the Kennedy Center Concert Hall. Violinist Jody Gatwood will perform s with the Prince George's Philharmonic, Saturday night at Prince George's Community College.

Masterpiece of the week: Bach's Mass in B minor, to be performed by the Washington Bach Consort, Friday night at the Kennedy Center. Bach's vocal music will also be on the agenda Saturday night at the University of Maryland, when the Bach Aria Group performs.

Duet of the week: Marilyn Horne and Montserrat Montserrat in openings rj Caballe' in an operatic program Saturday night in Constitution Hall. A very different kind of duet will be featured by the Montgomery Chamber Orchestra Saturday night at the National Bureau of Standards, with two Dutch double-bass virtuosos, Hans Roelofsen and Rudolf Senn, as guests.

Pianist Andre'-Michel Schub will be the National Symphony's guest soloist in an all-Brahms program thursday. Other notable pianists during the week will include Marc Ponthus, Wednesday night at the French Embassy, and Jeffrey Chappell, Wednesday afternoon at the World Bank.

Yoel Levi will continue as the NSO's guest conductor for a second week. His final performance of last week's program will be given on Tuesday night.

Music of John Dowland will be featured by the Folger Consort next weekend', with soprano Ann Monoyios among the guest artists. DANCE

The Houston Ballet makes its final appearance of its current Kennedy Center Opera House visit this afternoon, performing Ben Stevenson's full-length "Peer Gynt." American Ballroom Theater returns to the Kennedy Center's Terrace Theater for eight performances starting Tuesday evening. Also on Tuesday evening, the Dance Theatre of Harlem opens two weeks of performances at the Kennedy Center Opera House.Washington Ballet presents the premiere of Choo San Goh's "Unknown Territory," along with Goh's "Schubert Symphony" and Balanchine's "Serenade," in four performances at Lisner Thursday through Saturday. FILM

Opening Friday, Woody Allen's "Hannah and Her Sisters." A beautifully woven tale of three sisters living in New York, and the men who come into and go out of their lives, it's Allen's masterpiece. A must-see.

Also opening Friday, Ken Burns' "Huey Long," an artfully crafted documentary on the Louisiana populist who bequeathed us "Every Man a King."

Friday and Saturday at the American Film Institute, the Sleuths series continues with "The Thin Man," starring William Powell and Myrna Loy as Nick and Nora Charles. Thursday at the Hirshhorn Museum at noon, "Frank Stella," a walk-through with the artist of his 1984 retrospective at Harvard's Fogg Art Museum. Free.

The Down Under Festival continues this week with the Washington premieres of "Silver City" and "Heart of the Stag." Check your listings. The French Film Festival begins Friday at the K-B Janus with "L'Africain." Friday at 7:30 at the Library of Congress' Mary Pickford Theater, Orson Welles' "Chimes at Midnight" or "Falstaff." POP MUSIC

Bob Gibson, one of the key figures in the original folk revival, returns to the Birchmere on Tuesday.

Sri Chinmoy, the spiritual leader who has influenced such musicians as Carlos Santana, will present a Peace Concert at the Department of Commerce Auditorium on Thursday night.

On Friday and Saturday, the Smithsonian will present a symposium on "Black American Popular Music; Rhythm and Blues, 1945-1955." Along with an exhibit in the National Museum of American History's lower lobby , there will be a pair of free concerts featuring Paul (Hucklebuck) Williams (Friday) and Ruth Brown and the Orioles (Saturday) .

Producer/writer/musician August Darnell, aka Kid Creole, brings his Cocoanuts and his zany Caribbean pop to the Warner on Saturday. THEATER

Today is the last day to catch the Stratford Festival of Canada's charming production of "Twelfth Night" (at the Warner). Elsewhere, "Sally and Marsha" (Round House) and "Secret Honor" (New Playwrights') are worthy of attention. Coming up: Edward Duke's contagiously funny one-man show "Jeeves Takes Charge" (opening Wednesday at Ford's).