Tetrad (music)

In music theory, a "tetrad" is a set of four notes. When these four notes form a tertian chord they are more particularly and more commonly referred to as a "seventh chord", after the diatonic interval from the root of the chord to its fourth note (in root position close voicing). Four-note chords are often formed of intervals other than thirds in twentieth-century music, however, where they are more generally referred to as "tetrads" (see, for example, Howard Hanson's "Harmonic Materials of Modern Music: Resources of the Tempered Scale" and Carleton Gamer's, "Some Combinational Resources of Equal-Tempered Systems"). A four-note segment of a scale or twelve-tone row is more particularly known as a "tetrachord", although Allen Forte in his "The Structure of Atonal Music" uses the term "tetrachord" synonymously with "tetrad".

ee also

*Tetrachord
*Hexachord