Maynard Solomon, a musicologist and record producer best known for his influential biographies of Beethoven and Mozart, died Sept. 28 at his apartment in Manhattan. He was 90.

Maynard and his brother, Seymour, founded Vanguard Records. Over time, Vanguard and its Bach Guild label released an impressively diverse catalog of valuable recordings, especially folk music, blues and jazz. The classical repertory included English madrigals, Bach cantatas, masses by Haydn, and a landmark survey of the complete Mahler symphonies with Maurice Abravanel conducting the Utah Symphony Orchestra.

Mr. Solomon taught regularly at the Graduate Center of the City University of New York, Columbia, Harvard, Yale and the Juilliard School.