IT COULD have been quite a burden being regarded as the foremost champion of American music, but Aaron Copland seems to have borne it without much difficulty. Although he was once hailed by Leonard Bernstein as a "Moses," the composer who "would lead American music out of the wilderness," Mr. Copland, who died Sunday at the age of 90, took a more limited view of himself as just "one of a half-dozen pals who worked together to create serious music for America."

He was that, but he was also a dedicated artist who composed music over the course of a half-century, during which he produced both "difficult" pieces and the popular music for entertainments such as ballets and movies that most of us know him for. The fact that some of his compositions won a good deal less acclaim than others didn't bother him much. "He was as little dismayed by misunderstanding and neglect as he was spoilt by official honors," says The New Grove Dictionary of Music and Musicians.

Mr. Copland set out at a certain point in his career to create a type of music that was both thoroughly American and accessible to a large audience. Much of his best-known work had a strong western tinge -- "Billy the Kid," "Rodeo," "El Salon Mexico" -- which led some to joke that this son of immigrants, born and raised in New York, was trying to be a "cowboy from Brooklyn." But there was nothing artificial in Mr. Copland's treatment of the folk tunes and rhythms that he learned and incorporated into his work. He used them honestly and skillfully to evoke a sense of the countryside and of the people and their past -- as he did most successfully in the climactic passages of "Appalachian Spring" with its variations on a simple Shaker hymn.

"What I wrote was just the way I heard things," Mr. Copland once said. "I connect American sentiment with a certain reserve in its expression rather than something that carries its bleeding heart all over the place . . . One mustn't get too self-conscious about it all -- it has to come out as something quite natural. Then you can sit back and look at it and say, 'This is American music!' "