Correction: Mstislav Rostropovich sent word yesterday that he had read a story in The Sunday Washington Post concerning him and his dog, Pooks. "Tell him," he told the National Symphony press director, "I give him B-plus. Tell him I am absolutely NOT mad. Not mad. I know he is very busy music critic and does not have time to look . . ." Sunday's story called Pooks "him." Pooks - I apologize.

Speaking of the National Symphony, next week's program, to be given at the evening concerts on Tuesday, Wednesday, and Thursday, as well as at the first Friday matinee, is a real blockbuster. Leonard Bernstein will share the conductor's platform with Rostropovich, conducting the world premiere of Three Meditations from "Mass," for cello and orchestra, and the world premiere of Songfest, a work for six soloists and orchestra.

Rostropovich, in addition to playing in the Meditations, will conduct Bernstein's suite from the film "On the Waterfront." The singers in Sonfest's 14 songs will be Clamma Dale, Rosalind Elias, Nancy Williams, Neil Rosenshein, John Reardon and Donald Gramm.

Openings: On Sunday evening at 7:30, the Guarneri String Quartet will begin this year's University Community Concerts. Their program includes the first performance in the Washington area of the 1964 quartet by Witold Lutoslawski.

The Theater Chamber Players, who will move to their new home in the Kennedy Center next year, open their season on Monday night in Baird Autitorium with a gala program in which Pina Carmirelli will play both the E Major Partita of Bach and the G Major Sonata by Brahms. Leon Fleisher will conduct Schoenberg's Ode to Napoleon, for which Sunday's rehersal at 3:30 p.m. in the auditorium is open to the public without charge.

Sunday afternoon also marks the beginning, at the National Institutes of Health, of the NIH series, one of the brightest lists to be heard anywhere this year. The first offering, at 4 p.m., will be Monteverdi's "II Combattimento di Clorinda e Tancredi," with the New York Soloists under the artistic direction of Melvin Kaplan.

At the National Gallery's free concert at 7 p.m. Sunday, prize-winning tenor John Aler will sing a distinguished recital list.