FIRST OFF . . .

Lorin Maazel, music director of the Pittsburgh Symphony Orchestra, has agreed to a four-year extension of his contract. As a result, he will not perform the concert and recording dates he had been engaged to do with the Berlin Philharmonic through 1991. Last summer, Maazel was considered a leading candidate to succeed the late Herbert von Karajan as chief conductor of the Berlin Philharmonic, a position that earlier this month was awarded to Claudio Abbado, music director of the Vienna State Opera. Maazel also reiterated his resignation as music director of the National Orchestra of France effective Aug. 31, 1991. Maazel, 59, said his full energies will be devoted to the Pittsburgh Orchestra, which is currently winding up a four-week tour of the Soviet Union and Europe. His new contract will run through the 1995-96 season, the orchestra’s 100th anniversary.