MUSIC

The National Symphony Orchestra and conductor Mstislav Rostropovich go on their seventh foreign tour this summer--but Rostropovich, who defected from the Soviet Union in 1974, doesn’t think his motherland is on the itinerary. If Soviet authorities extend an invitation, he told reporters Tuesday, “then we will respond.” Rostropovich said he exchanged “polite words” with Soviet leader Mikhail S. Gorbachev at a White House state dinner during the December summit talks between Gorbachev and President Reagan, but that nothing serious was discussed.