 Specifically, Carter claims that he was guided by an all-interval tetrachord in the development of this work.In all my works from the Cello Sonata up through the Double Concerto I used specific chords mainly as unifying factors in the musical rhetoric—that is, as frequently recurring central sounds from which the different pitch material of the pieces was derived.For example, my First String Quartet is based on an "all-interval" four-note chord, which is used constantly, both vertically and occasionally as a motive to join all the intervals of the work into a characteristic sound whose presence is felt "through" all the very different kinds of linear intervallic writing.