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 stratification of material, with individual voices assigned not only their own unique pitch material but texture and rhythm as well, is a key component of Carter's style. His music after "Night Fantasies" has been termed his late period and his tonal language became less systematized and more intuitive, but retains the basic characteristics of his earlier works.