Born in Paterson, N.J. 63 years ago, Rochberg tried writing for Tin Pan Alley as a youth. But after being wounded in World War II, he bloomed as a serious composer and adopted the astringent, atonal, avant-garde form of the time, serialism. By 1963. however, Rochberg had disdained serialism's "overintense manner" that was alienating audiences and tormenting its creators. He resolved to regain contact with the music of the past. His search backward for melody, harmony and regular rhythmic pulse reached a zenith with the 1979 premiere of these works by the polished and vivacious Concord String Quartet, for whom he named the set in honor of their long association with his music. (The Concord, which is quartet-in-residence at Dartmouth College, took its own name from Charles Ives' Concord Piano Sonata.) These works parallel Rochberg's own professional journey, with dissonance and lyricism hotly debating each other in the Fourth and a rushing melodic exuberance beginning to dominate in the Fifth. The Sixth, the largest, devotes an entire movement to variations on Pachelbel's famous Canon and quotes Beethoven's Second String Quartet outright in the opening of the final movement. Rochberg pays homage to Mozart and Schubert too, yet the seams between present and past hardly show. Overall, the Concord Quartets are a complex, hopeful landmark in modern music.