Composer Aaron Copland was as old as the century and wrote the music that immortalized him by his (and the century's) mid-forties. He died two weeks after his 90th birthday party.
Mr. Copland wrote two strands of music. The first was up-to-the-minute, at least the minute of the 1920s when his education in composition took place. It was difficult, intellectual, modernist and had a lot to say to other composers and the musically literate. The other, inspired by his populist politics and his need to earn a living, was melodically accessible to all.
And when they are played, listeners say "American!" as readily as they say "Russian!" for Tchaikovsky and "Finnish!" for Sibelius. They also say "Copland!" because he was individualist as well as nationalist. His difficult music, some in a 12-tone scale, and his popular music, some of it soundtracks for movies, came from the same creative juices and musical knowledge.
All American composers put on their resume that they studied with Nadia Boulanger in Paris. He was the first. He learned how French the French composers were, and came back to sound as American. He wrote for every medium there was in his time, opera, symphony, ballet, modern dance, radio, movies.
Aaron Copland will be remembered for his popular stuff, "Billy the Kid," "Rodeo," "Appalachian Spring," "El Salon Mexico," "Lincoln Portrait" and "Fanfare for the Common Man." He quoted jazz and folk songs in large orchestral works before that was fashionable. Along with his contemporary, George Gershwin, he made it fashionable. Whether his more elusive music, such as Piano Variations, "Inscape" and Symphony No. 3, will also be played in 100 years, is less certain.
The period of nationalism in orchestral music is probably over. Aaron Copland outlived it, which may explain why he wrote nothing popular after the 1950s and nothing at all after the early 1970s. Yet he wrote about music, conducted and taught -- continuing to give to the musical life of the nation -- well into his eighties. To the extent that there is an American sound in the concert hall, Aaron Copland and a handful of others created it.