Music Theory--Chords

Chord

Chord, in music, three or more tones sounded simultaneously. Chords are classified according to the interval between their tones. The most common kind of chord is the triad, which is built of two consecutive thirds: If the bottom interval is a major third and the top one a minor third, the chord is a major triad (as, C-E-G). If the intervals are in the order minor third-major third, the chord is a minor triad (as, C-Eb-G or A-C-E). Less common are diminished triads (minor third plus minor third, as, C-Eb-Gb) and augmented triads (major third plus major third, as, C-E-G#). Triads can also be described as having the intervals of a third (such as C-E) and a fifth (C-G) formed with the root of the triad (here, C).

When additional thirds are piled on top of a triad, sevenths, ninths, elevenths, and other chords result; the interval between the bottom and top tones of a seventh chord is a seventh, hence the name of the chord. The most common seventh chord, called a dominant-seventh chord, consists of a major triad plus a minor third (as, G-B-D-F); it is so termed because it is the form of the seventh chord built on the fifth, or dominant, scale-note of a given key. Seventh chords can also be built of other major-minor combinations. One combination is the diminished-seventh chord (a diminished triad plus a minor third, that is, three minor thirds: G-Bb-Db-Fbb). Jazz musicians often use major seventh chords such as G-B-D-F# (major triad plus major third).

Chords have a strong aural identity, which they retain even when their tones are arranged in "inverted" order. Thus E-G-C (first inversion) and G-C-E (second inversion) are recognizable to the ear as versions of the C chord, C-E-G (normal or "root" position).

Other intervals such as fourths and seconds can also be used to construct chords. Composers such as the Russian Aleksandr Scriabin, the German Paul Hindemith, and the Hungarian Béla Bartók explored quartal harmony, or the use of chords built of fourths. Tone-clusters, or chords built of consecutive seconds, were used by the American composers Henry Cowell and Charles Ives.