Расширенные аккорды в музыке: теория и практика

chains of secondary dominants

In music, extended chords are certain chords (built from thirds) or triads with notes extended, or added, beyond the seventh. Ninth, eleventh, and thirteenth chords are extended chords. The thirteenth is the farthest extension diatonically possible as, by that point, all seven tonal degrees are represented within the chord (the next extension, the fifteenth, is the same as the root of the chord). In practice however, extended chords do not typically use all the chord members; when it is not altered, the fifth is often omitted, as are notes between the seventh and the highest note (i. e., the ninth is often omitted in an eleventh chord; the ninth and eleventh are usually omitted in a thirteenth chord), unless they are altered to give a special texture. Chords extended beyond the seventh are rarely seen in the Baroque era, and are used more frequently in the Classical era. The Romantic era saw greatly increased use of extended harmony. Extended harmony prior to the 20th century usually has dominant function – as V9, V11, and V13, or V9/V, V13/ii etc. Examples of the extended chords used as tonic harmonies include Wild Cherry's "Play That Funky Music" (either a dominant ninth or dominant thirteenth).

In the 18th century, ninth and eleventh chords were theorized as downward extensions of seventh chords, according to theories of supposition. In 1722, Jean Philippe Rameau first proposed the concept that ninth and eleventh chords are built from seventh chords by (the composer) placing a "supposed" bass one or two thirds below the fundamental bass or actual root of the chord. With the theoretical chord F–A–C–E–G–B the fundamental bass would be considered C, while the supposed bass would be F.

The theory of supposition was adopted and modified by Pierre Joseph Roussier, Friedrich Wilhelm Marpurg, and other theorists. A. F. C. Kollmann, following Johann Kirnberger, adopted a simpler approach and one closer to that prevalent today, in which Rameau's "supposed" bass is considered the fundamental and the ninth and eleventh are regarded as transient notes inessential to the structure of the chord.

In 19th century classical music the seventh chord was generally the upper limit in "chordal consonance", with ninth and eleventh chords being used for "extra power" but invariably with one or more notes treated as appoggiaturas. ]] In the 20th century, especially in jazz and popular music, ninth chords were used as elaborations of simpler chords, particularly as substitutes for the tonic triad at the end of a piece.

Jazz from the 1930s onward, jazz fusion from the 1970s onward and funk all have been seen to use extended chords as a key part of their sound. In these genres, chords often include added ninths, elevenths and thirteenths and altered variants, such as flat ninths, sharp ninths, sharp elevenths and flat thirteenths. In jazz and jazz fusion, compositions consist of complex chord progressions in which many of the chords are extended chords and in which many of the dominant seventh chords are altered extended chords (e. g., A7add911 or D7911). Funk also uses altered extended chords, but in this genre, pieces are usually based on a vamp on a single chord, because rhythm and groove are the key elements of the style. When extended chords are voiced in jazz or jazz fusion, the root and fifth are often omitted from the chord voicing, because the root is played by the bass player.