By 1970, using conventional notation, his distinctive doctrine of quietness, stillness and lack of dramatic rhetoric was fully in place. Feldman's best-known chamber works of this period include The Viola in My Life (1970-1971), Rothko Chapel (1971), and Why Patterns (1978). In his last compositions, Feldman became interested in the use of time and proportion. The resulting pieces became greatly expanded in scale, at least nine lasting more than ninety minutes. His composition For Philip Guston lasts four hours, and his String Quartet II can take up to six hours to perform. Yet even in his last works, Feldman's method is apparently intuitive, as he never admitted to, nor has any theorist been able to uncover, any systematic means of pitch selection.
Feldman's first teachers were Wallingford Riegger and Stefan Wolpe, but it was his meeting with John Cage in 1950 that set his entire future direction and musical aesthetic. Cage's circle of composers, which also included Christian Wolff and Earle Brown, combined with the influence of the visual artists that Feldman befriended, allowed him to develop his personal and instinctual method of composing. Feldman lived and worked in New York throughout most of his earlier creative career. In 1973, he was offered the Edgar Varèse Chair in composition at the University of New York at Buffalo, which he held until his death in 1987.