MENTION music, American music, classical music for most of the last half-century, and the name that leapt out was Leonard Bernstein, who died Sunday at age 72. As conductor, composer, popularizer, mentor and instrumentalist, he became the preeminent American musician of his time. He created the type. Before his sensational conducting debut in 1943, American music had been dominated by European models. The emerging Bernstein Americanized the muse. In his conducting, he personified the qualities of boldness and expressiveness. In his composing, he mined not only jazz and the popular culture but also the larger political scene for themes that brought him a vast nontraditional audience. When television came along to add the potential for visual immediacy to the pleasures of the ear, he was ready.

For the maestro, music was in the first instance the management of emotion. This was apparent to the millions who came into the Bernstein orbit. He went at directing a score as though he were its first interpreter, studying it deeply and only then stepping to the podium to use hands, face and body to choreograph the audience's response as well as the orchestra's. As someone with a political and intellectual range extending far beyond music, in his own works he took life at a point midway between imagination and mind. Unquestionably his best work was "West Side Story," which touched millions with truths of the street and soul and crowned an American popular-theater genre. His drive to communicate about music and extend its audience came through vividly in his television appearances.

Spreads himself too thin, they said about Leonard Bernstein, a bit too Broadway, not really among the greats. His gaudy personal style, including his heart-on-sleeve politics, set him up for countless putdowns. But if he did not create the considerable and varied body of distinguished pieces that makes a composer great, as a conductor and interpreter he operated consistently at the summit of musical achievement. His finest composition, and the work he conducted best, was his own personality. He felt music in every fiber, loved it prodigiously, was tormented by it and endlessly sought out ways to convey it to audiences great and small. This restless driven energy he communicated to a world public. It was his American essence.