In music theory, a
tetrad is a set of four notes. When these four notes form a
tertianIn music or music theory, tertian is the quality of a chord constructed from thirds, and other things constructed from thirds such as counterpoint. A third may be either minor or major...
chord they are more particularly and more commonly referred to as a
seventh chordA seventh chord is a chord consisting of a triad plus a note forming an interval of a seventh above the chord's root. When not otherwise specified, a "seventh chord" usually means a major triad with a flat seventh...
, 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 HansonHoward Harold Hanson was an American composer, conductor, educator, music theorist, and ardent champion of American classical music. Director for 40 years of the Eastman School of Music, he built a top quality school and provided unparalleled opportunities for commissioning and performing...
's
Harmonic Materials of Modern Music: Resources of the Tempered Scale and Carleton Gamer's, "Some Combinational Resources of Equal-Tempered Systems").
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In music theory, a
tetrad is a set of four notes. When these four notes form a
tertianIn music or music theory, tertian is the quality of a chord constructed from thirds, and other things constructed from thirds such as counterpoint. A third may be either minor or major...
chord they are more particularly and more commonly referred to as a
seventh chordA seventh chord is a chord consisting of a triad plus a note forming an interval of a seventh above the chord's root. When not otherwise specified, a "seventh chord" usually means a major triad with a flat seventh...
, 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 HansonHoward Harold Hanson was an American composer, conductor, educator, music theorist, and ardent champion of American classical music. Director for 40 years of the Eastman School of Music, he built a top quality school and provided unparalleled opportunities for commissioning and performing...
'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.