The National Symphony Orchestra will tour the Far East in spring of 1983, music director Mstislav Rostropovich said yesterday at a press conference on the 1982-1983 season. He also announced that the season will include a two-week festival of mostly little-known Scandinavian music.

Rostropovich will conduct in Washington during 10 weeks of the season but will not be present during the first six weeks, which will be led by principal guest conductor Rafael Fru hbeck de Burgos. Rostropovich said he is committed to remain in Paris until late November in order to conduct 11 performances of Tchaikovsky's "Eugen Onegin" at the Paris Opera.

Among the new works of the season are "Tenebrae" for cello and orchestra by Norwegian composer Arne Nordheim (with Rostropovich as the soloist), a symphony by Hans Abrahamsen of Denmark, and untitled commissioned works by Icelandic composer Jon Nordal, the Finn Aulis Sallinen and the Swede Ingvar Lidholm. Other new works will be by Washington composer Stephen Burton and by Jacob Druckman, another American composer. The latter was scheduled for this year, but Rostropovich said that "for technical reasons he is not ready to finish it this season." The substitute for the Druckman this year will be "Lines from Isaiah," a symphony with voice by Ezra Laderman, director of the music program at the National Endowment for the Arts.

Other novelties include a performance by bassist Gary Karr of the Contrabass concerto of Serge Koussevitzky, who played the bass before he became a conductor; a concert conducted by flutist Jean-Pierre Rampal in which he will also join NSO first flutist Toshiko Kohno in Cimarosa's Sinfonia concertante for two flutes, and a performance of the rarely heard violin concerto of Polish composer Karol Szymanowski, in observance of his 100th birthday.

The Far East tour, scheduled for April 8 to April 27, 1983, will include the Japanese cities of Osaka, Nagoya and Tokyo, as well as Manila, Taipei, Seoul and Hong Kong. The National Symphony made its first tour of the Orient in 1980.

In addition to Rampal, there will be five guest conductors next season: Eugene Ormandy, Max Rudolf, David Zinman, Christopher Keene and Peter Maag. Both Zinman and Maag will be leading the orchestra for the first time.

Among the special events will be a performance of the grim Shostakovich Symphony No. 14, with Rostropovich's wife, soprano Galina Vishnevskaya, and British bass Stafford Dean as soloists. The Mahler Second Symphony will close the season, with the NSO joined by the Choral Arts Society, soprano Ellen Shade and mezzo Claudine Carlson.

Soloists appearing for the first time with the orchestra include Karr, Dean, cellist Frans Helmerson, baritone Dominic Cossa, tenor David Britton, duo-pianists Richard and John Conti-Guglia, and pianists Raymond Lewenthal, Ivan Moravec and Bella Davidovich.