FIRST OFF . . .

The Los Angeles Philharmonic Assn. said Andre Previn, music director of the orchestra, has signed a contract extension to June, 1991. Previn assumed directorship of the Philharmonic in January, 1986, after beginning the 1985-86 season as director-designate. The extension calls for the conductor’s residency with the orchestra for a minimum of 14 weeks in the winter season at the Dorothy Chandler Pavilion and two weeks during the summer at Hollywood Bowl, plus tours, recordings and special projects.