What is "trichord"

Trichord \Tri"chord\, n. [Gr. ? three stringed; ? (see Tri-) + ? chord, or string.] (Mus.) An instrument, as a lyre or harp, having three strings.

n. 1 (context music English) any set of three different pitch classes 2 A musical instrument with three strings, such as a lyre or harp.

In music theory, a trichord is a group of three different pitch classes found within a larger group . For example a contiguous three-note set from a musical scale or a twelve- tone row. The term is derived by analogy from the 20th-century use of the word " tetrachord". Unlike the tetrachord and hexachord, there is no traditional standard scale arrangement of three notes, nor is the trichord necessarily thought of as a harmonic entity .

Just as a diatonic scale is conventionally said to be constructed of two disjunct tetrachords (CDEF+GABC=CDEFGABC), a pentatonic scale can be constructed of two disjunct trichords (ACD+EGA=ACDEGA; GAC+DEG=GACDEG).

Milton Babbitt's serial theory of combinatoriality makes much of the properties of three-note, four-note, and six-note segments of a twelve-tone row, which he calls, respectively, trichords, tetrachords, and hexachords, extending the traditional sense of the terms and retaining their implication of contiguity. He usually reserves the term "source set" for their unordered counterparts (especially hexachords), but does occasionally employ terms such as "source tetrachords" and "combinatorial trichords, tetrachords, and hexachords" instead (; ; ).

Allen Forte occasionally makes informal use of the term trichord to mean what he usually calls "sets of three elements" , and other theorists (notably including Howard , and Carlton ), mean by the term triad, a three-note pitch collection which is not necessarily a contiguous segment of a scale or a tone row and not necessarily (in twentieth-century music) tertian or diatonic either.