That Elliott Carter was still creating music as a centenarian--he completed his last work in August--is less impressive than that his music is still in demand. Carter, who died Nov. 5 at 103, began composing in the 1930s and never stopped; he wrote more than 40 pieces between ages 90 and 100. His String Quartet No. 1, in 1951, was a breakout work, while the second and third quartets won him the Pulitzer Prize in 1960 and 1973. Four were recorded by the Juilliard String Quartet to mark its 45th anniversary in 1991. (String Quartet No. 5 came in 1995.) His rhythmically complex work is not easy listening--the quartets have been called the most difficult music ever conceived--but those who take the time to understand it are richly rewarded.