The time of next Saturday's concert by the American Chamber Orchestra at the National Academy of Sciences was incorrect in Sunday's Show section. It will be at 3 p.m.

ART

"Treasure Houses of Britain," opening today in the National Gallery of Art's East Wing, celebrates art collecting and patronage by the owners of "country houses" in Great Britain. CLASSICAL MUSIC

American Music Week, beginning tomorrow, will be observed with dozens of concerts in the Washington area, mostly on university campuses and far too numerous to list. It will offer connoisseurs an opportunity to hear much seldom-heard repertoire; for example, a program of piano music by black composers Wednesday at Howard University and a program of classical music for mandolin, Saturday afternoon at the Dumbarton Avenue Methodist Church. Other rarely heard music this week will include the work of two women composers, Loretta Jankowski and Katherine Hoover, performed by the New Jersey Chamber Music Society today at the Corcoran Gallery. Canteloube's "Songs of the Auvergne," including some of the most beautiful melodies ever composed for the soprano voice, will be on Friday's free lunch-hour program, sponsored by the Friday Morning Music Club at the New York Avenue Presbyterian Church.

The Washington Opera opens its final production of the Opera House season Saturday night: Verdi's "A Masked Ball," which is well-remembered from its previous run in 1980. The shortened season in the Terrace Theater will not begin until December.

Rafael Fru hbeck de Burgos will conduct the National Symphony in a program of Beethoven, Saint-Sae ns and Ibert, beginning Thursday night, with Jeffrey Kahane as piano soloist.

Distinguished visitors of the week include the Vienna Symphony, Wednesday night at the Kennedy Center; the New Irish Chamber Orchestra, Tuesday night in the Terrace Theater; the Waverly Consort, Friday night at the Library of Congress; pianist Nikita Magaloff, Thursday night in the Terrace Theater; cellist Aurora Natola-Ginastera, tomorrow night in the Terrace Theater; the Eder String Quartet, Saturday afternoon at the Library of Congress; the Golub-Kaplan-Carr Trio, Saturday night at the University of Maryland's Adult Education Center.

The Washington Music Ensemble will give a concert in the Terrace Theater today as part of its French Music Festival. And the Montgomery Chamber Orchestra will perform music of Mozart, Copland and Brahms Saturday night at the Bureau of Standards in Gaithersburg. DANCE

Cloudgate, Taipei Contemporary Dance Theatre, under the direction of Lin Hwai-Min, appears at Lisner Auditorium in "Dreamscape," inspired by Dunhuang murals of the Tang Dynasty, on Monday and Wednesday evenings, and in "Legacy," depicting the settling of Taiwan by Chinese pioneers, on Tuesday evening. Choreographer Lin blends Chinese folk dance with the modern dance techniques of Martha Graham, Merce Cunningham and others. The Wendy Osserman Dance Company, founded 10 years ago in New York, makes its Washington debut at the Dance Place Friday and Saturday in a program of works by Osserman to such composers as Brian Eno, David Byrne and others. The "Dance America" series brings the Washington debut of the Mark Morris Dance Group to the Kennedy Center's Terrace Theater Saturday and Sunday. A native of Seattle, the profusely inventive Morris has become the widely heralded young choreographer in the nation in the few years since he burst upon the contemporary scene. FILM

The Dead of Night Horror Film Festival continues tonight at the Circle Theater with Werner Herzog's dazzling "Nosferatu," in repertory with the eminently missable "The Company of Wolves." Tomorrow, Ray Harryhausen's influential "The Seventh Voyage of Sinbad" and "Jason and the Argonauts." Wednesday, Hammer studio's "Curse of the Werewolf" and "Dracula Has Risen From the Grave" -- a must-see.

The Zany Comedy series continues at the American Film Institute tonight with "The Court Jester," starring Danny Kaye, along with Three Stooges shorts; tomorrow, Charlie Chaplin's "The Gold Rush" and "The Cure"; Friday, Laurel and Hardy in "Sons of the Desert" and "Way Out West." The Black Hollywood Post World War II series begins tomorrow night at the University of the District of Columbia with Mark Robson's "Home of the Brave." Free. Call 727-2396 for details.

The National Archives War Film series continues Friday at noon with "Swastika," a British documentary chronicling the private lives of the Nazi leadership. Free. Call 523-3000 for details.

Tonight and tomorrow at the Biograph, "Moscow Does Not Believe in Tears."

Saturday, the Surrealist Cinema series at the Corcoran Gallery continues with Luis Bun uel's "L'Age d'Or." The locus classicus of surrealism. Call 638-3211 for details.

Among current releases, Martin Scorsese's brilliant, if flawed, "After Hours"; Emir Kusturica's tender, funny "When Father Was Away on Business." POP MUSIC

Morris Day, a truly sharp-dressed man and R&B bon vivant, brings his immensely danceable music to the Washington Convention Center tonight, with groovemeisters Atlantic Starr and Maryland's own very hot Starpoint.

A good week for overseas rock bands, with Scotland's Simple Minds and Shriekback at Constitution Hall on Monday, and Everything But the Girl, Blue in Heaven (also from Scotland) and Robyn Hitchcock and the Egyptians at the 9:30 club (Thursday, Friday and Saturday, respectively).

John Renbourn, ex-Pentangle founder, teams with fellow guitarist Stefan Grossman in a rare concert appearance at the Birchmere on Wednesday. THEATER

In " 'night Mother"(at Arena's Kreeger Theater), a daughter announces to her mother that she has decided to commit suicide. Putting all philosophical questions aside, Pulitzer Prize-winning playwright Marsha Norman chronicles the 90 humble, occasionally funny, minutes that follow. Superlatively acted and meticulously staged, the evening builds to a devastating climax that will send you reeling from the theater.