The glory of Leonard Bernstein's talent was also its shortcoming: Everything came so easily to him that he seldom had to settle down to the kind of hard work that distinguishes transcendently great work from that which is merely very good. He was a composer who reached the heights of popularity, a conductor whose name was familiar wherever classical music was known and loved, a pianist of formidable technique and great expressive power, a teacher who revolutionized the ways of presenting classical music to new audiences and, pioneering the medium of television, showed later arts and education programmers how it should be done.

During the nationwide celebration of his 70th birthday two years ago, he said, "I've achieved more than I had any right to expect. Nobody has been as lucky as I have." And he was surely right.

Still, his death yesterday of emphysema and other lung problems left an uneasy feeling that his full potential had never been quite realized. Part of the reason for this is that nobody could develop so many talents in one lifetime with the limited energy of a single human being. But part of it was rooted in the fact that he did not focus and refine his talents. He certainly did not wish to do this, and possibly could not. His refusal to settle for less than everything was reflected not only in his career but also in his lifestyle. Besides being the most prominent American musician of his time in many fields, he was a social lion, occasionally a radical political activist. His vigorous bisexual orientation did not prevent him from being an extraordinarily devoted husband to Chilean actress Felicia Montealegre, who died in 1978, and a loving father to their three children.

His problem was never a lack of identity, as it can be with those who are unable or unwilling to focus their lives; instead it was a surplus of identities -- an impressive list of accomplishments in many areas.

As a composer, he was at home in jazz, the pop techniques of Broadway, Latin dance idioms, post-Stravinsky ballet styles, symphonic music for virtuoso orchestra, choral music of intensely religious feeling, chamber music, works for solo piano and songs in a wide variety of styles and idioms, with piano or orchestral accompaniment. Whatever he did was done with flair, and usually it appealed to a vast audience, though some of his work (notably the musical "1600 Pennsylvania Avenue" and the opera "A Quiet Place") got largely negative reactions from critics and the public, and some (including his "Slava!" Overture, composed for the National Symphony Orchestra and Mstislav Rostropovich) had more flash than substance.

But his list of major works, and probably works of lasting value, is a long one. He was particularly adept at theatrical-dramatic works, begining with the ballet "Fancy Free" and the musical "On the Town" in 1944, also including the one-act opera "Trouble in Tahiti" (1951), the musical "Wonderful Town" (1953), the soundtrack for "On the Waterfront" (1954), the operetta "Candide" (1956), the musical theater piece "Mass" (composed for the opening of the Kennedy Center in 1971) and the ballet "Dybbuk" (1974). All of these are music of value, but his greatest effort in theatrical music and probably his most enduring monument is the musical "West Side Story," a powerful updating of the Romeo and Juliet story that uses popular dance and classical forms as well as standard Broadway styles with remarkable unity of effect.

Outside the theater, he first made a strong impression with his "Jeremiah" Symphony, introducing a Jewish element that runs through his music from his Third Symphony ("Kaddish") to his "Chichester Psalms" with Hebrew texts. Other works that are likely to endure include his Second Symphony ("The Age of Anxiety") with a powerful part for solo piano, his Serenade (inspired by Plato's "Symposium") for violin, harp, strings and percussion, "Halil," a nocturne for flute and strings, and his most recent work, a song cycle titled "Arias and Barcarolles" that ranges through a wide variety of styles showing expertise in all of them.

As an educator, his best work is preserved in two books, "The Joy of Music" (1959, revised and enlarged as "Young People's Concerts" in 1970) and "The Unanswered Question" (1976, the text of the Norton Lectures he delivered at Harvard). A more careless side of his work is to be found in his last book, "Findings" (1982), a random collection of writings ranging in date from 1935, when he was a high school student at Boston Latin to a commencement speech given at Johns Hopkins University in 1980.

As a conductor, Bernstein could do well with everything from Mozart and Haydn, through Beethoven, Schumann and Brahms, up to the music of such 20th-century masters as Copland and Stravinsky, both of whom influenced his own work as a composer. He may have made his strongest mark, however, as an interpreter of Gustav Mahler, and he was probably the strongest single force in the revival of Mahler's work during the past 30 years.

His conducting style often leaned toward Dionysian frenzy but was sometimes superbly tranquil and occasionally totally self-effacing -- he would simply stand motionless while his orchestra played, communicating with the players (and often the television audience) mostly through the emotions playing across his expressive face. As a conductor, he was in great demand and, at one time or another, conducted virtually all the great orchestras in the world. He was particularly at home, however, with the Vienna, Berlin, New York and Israel Philharmonic orchestras and the London Symphony in his later years, when he had become the most eagerly sought guest conductor in the world and one of the hardest to get.

He first reached the public eye and the top of his profession at his unexpected debut on Nov. 14, 1943, when conductor Bruno Walter was stricken ill and Bernstein, then age 25, stepped in at the last minute to conduct the New York Philharmonic, dazzling the audience and critics. His debut was front-page news in the New York Times the next morning, and he never left the spotlight.

He was appointed the music director of the Philharmonic in 1957 (the first and, so far, the only American to hold that position) and directed the orchestra for 12 years before resigning to become a freelance conductor.

For years, Bernstein refused to record in a studio, and his Vienna recordings have had the virtues and problems of his live performances -- a sense of spontaneity and excitement as well as occasional overstatement. The last time he conducted was was on Aug. 19, a few days before his 72nd birthday, at the Koussevitzky Memorial Concert in at Tanglewood in Lenox, Mass.

Last week, he announced that he was retiring from conducting because of emphysema and other lung ailments. Optimistic to the end, he announced that he planned to continue work as a composer after recovering his strength.