Trichord

Depending on the context, a "trichord" is either a contiguous segment of a musical scale or of a twelve-tone row, or (in accord with Allen Forte's redefinition of the term) a musical "triad", that is, any three-note pitch collection.

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.

Allen Forte in his "The Structure of Atonal Music" redefines the term "trichord" to mean what other theorists (notably including Howard Hanson in his "Harmonic Materials of Modern Music: Resources of the Tempered Scale" and Carlton Gamer in his "Some Combinational Resources of Equal-Tempered Systems") 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.

ee also

*Triad

References

* Forte, Allen (1977) "The Structure of Atonal Music", Yale University Press.
* Gamer, Carleton (1967) Some Combinational Resources of Equal-Tempered Systems, "Journal of Music Theory", Vol. 11, No. 1 (Spring, 1967), pp. 32-59.
* Hanson, Howard (1960) "Harmonic materials of modern music", Irvington.