by elaborate rhythmic layering and metric modulation. While Carter's chromaticism and tonal vocabulary parallels serial composers of the period, Carter did not use serial techniques. Carter said, "I certainly have never used a twelve-tone row as the basis of a composition, in the way described in Schoenberg’s Style and Idea, nor are my compositions a constant rotation of various permutations of twelve-tone rows". Rather, he independently developed and catalogued all possible collections of pitches (i.e., all possible three-note chords, five-note chords, etc.), compiling what he called his Harmony Book. (An edited version of the book was published in 2002 by Carl Fischer Music.) Musical theorists like Allen Forte independently had systematized these data into musical set theory perhaps having been inspired by Howard Hanson's Harmonic Materials of Modern Music. A series of Carter's works in the 1960s and 1970s generates its tonal material by using all possible chords of a particular number of pitches. Among his better known works are the Variations for Orchestra (1954–55); the Double Concerto for Harpsichord and Piano with Two Chamber Orchestras (1959–61); the Piano Concerto (1964–65), written as an 85th-birthday present for Stravinsky; the Concerto for Orchestra (1969), loosely based on a poem by Saint-John Perse; and the Symphony of Three Orchestras (1976). He also composed five string quartets, of which the second and third won the Pulitzer Prize for Music in 1960 and 1973 respectively. Spaced at regular intervals throughout his mature career, they are considered by some to be the most important body of work in that medium since Bartók. Symphonia: sum fluxae pretium spei (1993–96) is his largest orchestral work, complex in structure and featuring contrasting layers of instrumental textures, from delicate wind solos to crashing brass and percussion outbursts. The Piano Concerto (1964–65) uses the collection of three-note chords for its pitch material; the Third String Quartet (1971) uses all four-note chords; the Concerto for Orchestra (1969) all five-note chords; and A Symphony of Three Orchestras uses the collection of six-note chords. Carter also made frequent use of "tonic" 12-note chords. Of particular interest are "all-interval" 12-tone chords, where every interval is represented within adjacent notes of the chord. His 1980 solo piano work Night Fantasies uses the entire collection of the 88 symmetrical-inverted all-interval 12-note chords. Typically, the pitch material is segmented between instruments, with a unique set of chords or sets assigned to each instrument or orchestral section. This