Klaus Tennstedt, widely heralded German conductor, will make his National Symphony debut this week, leading the orchestra in its Tuesday-Wednesday night subscription concerts. For his program he has chosen two superb and widely contrasting works: the Second Piano Concerto of Prokofiev, with Horacio Gutierrez as soloist, and the Fourth Symphony by Bruckner.

Speaking of Bruckner, his Eighth Symphony will be on Friday night's program by the Zurich Tonhalle Orchestra, led by Gerd Albrecht, who will also conduct three Night Pieces by Heinz Holliger, and the Second Piano Concerto by Beethoven, with soloist Justus Frantz. The Bruckner Fourth will return again next month when Eugene Ormandy leads the Philadelphia Orchestra in it on March 7.

Murry Sidlin will conduct the National Symphony's Thursday night concert, Feb. 10, in place of Andre Kostelanetz, who is recovering from viral pneumonia. Sidlin's soloists will be the Golabek sisters, Mona and Renee, playing the Poulenc Concerto.

Notes for string players: The annual D.C. Federation of Musicians string competition will be held on March 18. Players of violin, viola, cello, and double bass, between the ages of 16 and 23, will compete for full scholarships to the 19th Annual Congress of Strings, to be held from June 20 through Aug. 19. In addition to the usual two scholarships, there will be a third, given to a double bass player in memory of Joe Willens, for many years one of the top bass players in Washington. For details and applications, write to Robert D'Arcy, Secretary, Local 161-710, A.F.M., 5020 Wisconsin Ave. NW, Washington, D.C. 20016.

Artur Rubinstein is president of a new board established to set up a Lionel Tertis Viola Competition in memory of Tertis, who died early in 1975, at the age of 98. Born on the same day as Pablo Casals, Tertis accomplished on the viola much of the same revival of interest and establishment of standards of playing that his colleague did on the cello. Donations may be sent to the Royal Philharmonic Society, 124 Wigmore Street, London W1 M OAX, England.

Violinist Daniel Heifetz will play a recital in the Jewish Community Center at 8 p.m., Sunday, Feb. 13, appear as soloist with the Philadelphia Orchestra in Kennedy Center on April 18, and make his New York debut in an Alice Tully Hall recital on April 26. Tickets for the JCC concert available at the door.

Brazilian pianist Nelson Freire, who plays in the Kennedy Center on Saturday night, Feb. 12, made an extraordinary impression last year at the University of Maryland. He will play Liszt, Ravel, Villa-Lobos, and Chopin.