The National Symphony Orchestra and Paris-based Erato Records have negotiated a three-year, seven-record recording contract, the largest in the 10-year tenure of music director Mstislav Rostropovich.

Two of the seven records will be taped this season, in conjunction with concerts by the NSO. The first, to be taped today and Saturday in the Kennedy Center Concert Hall, will be devoted to Shostakovich's 13th Symphony, "Babi Yar," which the orchestra is performing on this week's program with the men of the Choral Arts Society and Bulgarian bass Nicolai Ghiuselev.

The second recording session, planned for the first week of March, will tape that week's program, with violin soloist Anne-Sophie Mutter: Glazunov's Violin Concerto, Prokofiev's Violin Concerto No. 1 and Prokofiev's "Russian" Overture.

The NSO has already made one recording for Erato: Modest Mussorgsky's opera "Boris Godunov," which was taped last summer at the Kennedy Center with an international cast of singers. It will be used as the sound track of a movie that's scheduled to open the 1989 Cannes Film Festival. Like all Erato recordings, those made by the NSO will be distributed in the United States by RCA Victor.

Repertoire is still being discussed for the five remaining records, but all will be conducted by Rostropovich, who has long been associated with Erato both as a cellist and as a conductor. His Erato discography comprises more than a dozen records, including eight works for cello and orchestra, a complete cycle of Prokofiev's symphonies (mostly still unreleased), Rachmaninoff's Vespers with mezzo soprano Maureen Forrester, tenor Gene Tucker and the Choral Arts Society, and several operas featuring soprano Galina Vishnevskaya, Rostropovich's wife. Two of them, Prokofiev's "War and Peace" and Mussorgsky's "Boris Godunov," are still unreleased.

The "Boris" recording sessions last summer "went extremely well," and that led to the new contract, according to Erato Executive Vice President Fre'de'ric Sichler.

"Everything came together," he said. "The incredible level of the interpretation by the National Symphony under Slava's baton, the excellent acoustics of the Kennedy Center Concert Hall, the total and efficient support of the NSO administrative team ... Michel Garcin {founder and artistic director of Erato} and his artistic and engineering colleagues had scarcely found comparable conditions in the past. No question, it was the beginning of a long-term project."

Rostropovich hailed the contract as "very good news" for the NSO. "Establishment of a strong recording presence is vital to the orchestra's further growth," he said, adding that Erato produces "recordings of the very highest quality."

It is significant that the first two sessions include music of Shostakovich and Prokofiev, the two greatest Russian composers of the 20th century, both of whom were close friends of Rostropovich's and composed cello works for him. Rostropovich has already conducted most of Shostakovich's 15 symphonies with the NSO, and has often expressed his interest in recording the entire cycle, preferably with the NSO. Erato has none of the Shostakovich symphonies in its current catalogue, and a complete Shostakovich cycle conducted by Rostropovich would be a logical sequel to its complete Prokofiev cycle under the same conductor. No plans have been announced, however, beyond that of recording Shostakovich's 13th this week.