Sixth chord

In music, a sixth chord is any chord, or meaningful connection of notes, that contains the interval of a sixth.

The simplest example is the first inversion of a minor triad, which consists of a major third and a major sixth above the root; when the term sixth chord is used without qualification, it usually refers to such a chord. In early music this was considered an autonomous harmonic entity with the root named by the bass, while after this period it was simply considered an inversion of a chord with the bass being the third (not the root) and the root being the sixth (not the bass). In jazz, this form is referred to as a major sixth chord.

There are also a number of non-standard sixth chords. The "added sixth chord", as the name suggests, is a triad with an added sixth. It is generally built on the sub-dominant (fourth scale degree), although they can be built on any note. An added sixth chord built on C consists of the notes C, E, G, and the added sixth A Play^ⓘ. These are the same notes as those of an A minor seventh chord - whether such a chord should be regarded as an added sixth chord or a seventh depends on its context and harmonic function. To explain the analyses as added sixth chords, against common practice period theory, Cope (1997) provides the example of the final tonic chord of some popular music being traditionally analyzable as a "submediant six-five chord" (added sixth chords by popular terminology), or a first inversion seventh chord (possibly the dominant of the mediant V/iii). According to the interval strengths of the added sixth chord the root of the strongest interval of the chord in first inversion (CEGA), the perfect fifth (C-G), is the bottom (C), the tonic.

In jazz, the minor sixth chord (sometimes: minor (major sixth), analogous to minor (major seventh)) is frequently used. It is unlike the major sixth chord, which is often substituted for a major triad; the minor sixth plays a number of different harmonic roles. The chord consists of a minor triad with an added major sixth tone; thus in C, it would contain the notes C, Eb, G, and A. This chord might be notated Cm6, Cm/M6, Cmin/Maj6, C min (Maj6), etc. Note that Cmin(Maj6) has the same notes as F9 with the root omitted, i.e. the notes F (omitted), A, Eb, C, and G. These notes form a tetrad with several enharmonic equivalents: C/Eb/G/A might be written as Cmin(maj6), F9, F9 (no root), Am7b5, B7b9, or B-alt. Many jazz chord charts use these chord notations indiscriminately, particularly in the choice of minor sixth versus dominant ninth chords. Thus, in some cases when a Cm6 is indicated, the F9 is in fact a better harmonic choice, i.e. closer to the composer's harmonic intent; or vice versa. Analysis of the movement of the root tone, and the present of dominant harmonies, will generally indicate which enharmonic chord is the appropriate notation choice. In some cases, the harmony is ambiguous.

The Neapolitan sixth is the first inversion of a major triad built on the flattened supertonic (second degree of the scale) - a Neapolitan sixth in C major, therefore, consists of the notes F, A flat and D flat. Neapolitan sixth chord preceding authentic cadence (V-I)^ⓘ

There are a number of augmented sixth chords. Each of them has a major third and augmented sixth above the bass. When these are the only three notes present, the chord is an Italian sixth Italian sixth moving to V.^ⓘ; when an augmented fourth is added above the bass, the chord is a French sixth French sixth moving to V.^ⓘ; while adding a perfect fifth above the bass of an Italian sixth makes it a German sixth German sixth moving to V^ⓘ (the etymology of all these names is unclear). All usually have the flattened sub-mediant (sixth degree of the scale, A flat in C major, for example) as the bass note -in this case, they tend to resolve to the dominant.

Source

Cope, David (1997). Techniques of the Contemporary Composer, p.40-41. New York, New York: Schirmer Books. ISBN 0-02-864737-8.