Seventh Chords & Extended Harmonies

Image Description. American jazz pianist Annie Booth performs in Denver in 2021. Jazz pianists parts use many complex chords in different voicings to establish a harmonic texture to support other musicians' improvisation.
(Glenn Booth | CC BY-SA-4.0)

A chord with four notes is called a tetrad. Because tertial tetrads — four-note chords built using major and minor thirds — contain a note which is a seventh above the root, these chords are more commonly called seventh chords.

Types of Seventh Chords

By using major and minor thirds, we can create eight possible types of seventh chords. Seventh chords are often labeled using two terms: the type of triad to start from and the type of seventh to add above the root.

Figure 1: Seventh chord types are determined by the intervals that comprise the chord, and are named for the triad formed by the bottom three notes and the interval from the root to seventh of the chord.

Major-major seventh chords are generally referred to as major seventh chords; likewise, minor-minor seventh chords are simply called minor seventh chords. Diminished-diminished seventh chords are commonly called fully diminished seventh chords, while diminished-minor chords are generally called half-diminished seventh chords.

Of the eight possible seventh chords, the minor-major seventh chord and the augmented-major seventh chord are rarely used, and the augmented-augmented seventh chord is enharmonically equivalent to an augmented triad with a doubled root.

An E flat augmented-augmented chord, spelled E flat, G, B, D sharp, and an E flat augmented triad with a doubled root, spelled E flat, G, B, E flat.
Figure 2: An augmented-augmented seventh contains an augmented seventh, which is enharmonically equivalent to a perfect octave, so it sounds like an augmented triad with a doubled root.

In addition to root position, first inversion and second inversion, seventh chords can appear in third inversion, in which the seventh of the chord is the lowest sounding voice.

A D minor seventh chord spelled four different ways: with a D in the bass, an F in the bass, an A in the bass, and a C in the bass.
Figure 3: Seventh chords can appear in four different positions: root position, first inversion, second inversion and third inversion. As with triads, inversions are determined only by which note appears in the lowest position.

Extended Harmonies

Within tertial harmony, it is possible to continue adding thirds to create pentads, hexads, and heptads, which are more commonly known as ninth chords, eleventh chords and thirteenth chords. Further additions are not generally considered because they result in duplicate notes.

A C nine chord, C eleven chord, C thirteen chord and C fifteen chord shown on the staff. The C nine chord consists of C4, E4, G4, B4 and D5; the C eleven chord adds F5, the C thirteen chord adds A5, and the C fifteen chord adds C6. In the last chord, C4 and C6 are highlighted as being the same pitch class.
Figure 4: Extended harmonies built on C, using the notes of the C major scale. Extended harmonies beyond the thirteenth are generally considered to be forms of lower chords with doubled notes; in this case, the C15 chord would be interpreted as a C13 with a doubled root.

While these chords can be named using the same system as seventh chords, the names can are unwieldy and rarely used. Because of this, theorists usually use a naming system drawn from jazz genres, which is further described in Harmonic Analysis.

Figure 5: Extended harmonies. Combining triads, seventh chords, and all extended harmonies created by stacking major and minor thirds, there are 124 possibilities, not counting chords with missing notes.

Depending on the type of chord, extended harmonies can be placed in positions up to fourth, fifth, and sixth inversion, with the ninth, eleventh or thirteenth of the chord placed in the bass, respectively.

A chord spelled G B D F A C E and labelled as G thirteen in root position, and another chord spelled B D F A C E G labelled as G thirteen in first inversion or B thirteen in root position.
Figure 6: Extended harmonies can appear in inversions. Because of the large number of pitch classes used, inverted arrangements can sometimes be aurally similar or identical to root position arrangements.

Not all notes in these large chords are always included. When selecting which voices to leave out, composers and arrangers almost always include at least the following:

  • the root, which defines the foundation of the chord,
  • the third, which gives the chord a tertial quality and characterizes is as major or minor,
  • the highest chord member, which defines the chord as a ninth, eleventh or thirteenth, and
  • the seventh, which acts as an aural "bridge" connecting the extended harmonies.
A chord spelled C E G B D F A, with the G, D and F grayed out. The A is labeled `13th - establishes quality of chord`, the B is labelled `7th - connects to extended harmony`, the E is labeled `3rd - establishes tertial character`, and the C is labelled `root - defines harmonic foundation`.
Figure 7: In extended harmonies, the fifth and notes between the seventh and the highest factor can be omitted without sacrificing the character of the chord.

Other Chords

Other types of chords that are common in some 12-TET styles include:

  • chords with added seconds, fourths, or sixths, which are often called add 2, add 4 or add 6 chords, respectively,
  • triads where the third is replaced by a fourth above the root, called a sus chord,
  • triads where the third is replaced by a second above the root, called a sus 2 chord,
  • dyads consisting only of the root and a perfect fifth above the root, called open fifth chords or power chords, and
  • ninth chords which contain a sixth above the root in place of a seventh above the root, called 6/9 chords.
Several different chords shown in staff notation: triads with an added second, an added fourth, and an aded sixth, a sus 2 and a sus 4 chord, a power chord, and a 6/9 chord.
Figure 8: Some 12-TET styles use chords that deviate from the standard pattern of stacking major and minor thirds.

Seventh Chords & Extended Harmonies: Summary

  • A chord with four notes is called a tetrad, but tertial triads are more commonly called seventh chords.
  • There are eight different possible seventh chords in the 12-TET system.
    • Seventh chords are usually labelled in two parts: the name of the triad used and the type of seventh added above the root.
    • Major-major seventh chords and minor-minor seventh chords are commonly called major seventh chords and minor seventh chords, respectively.
    • Diminished-minor seventh chords and diminished-diminished seventh chords are commonly called half-diminished seventh chords and fully diminished seventh chords, respectively.
  • Seventh chords can be placed in root position, first inversion, second inversion, or third inversion.
  • Chords with added ninths, elevenths, or thirteenths above the root are called extended harmonies.
    • The thirteenth is the furthest possible harmonic extension, since a fifteenth simply doubles the root.
    • Extended harmonies can be placed in inversions up to sixth inversion, but are less aurally distinctive.
    • Composers and arrangers often omit chord tones from extended harmonies, but generally retain at least the root, third, seventh, and whatever note is the furthest extension in the chord.
  • Examples of chords in 12-TET styles that are not limited to stacked major and minor thirds include chords with added notes, sus chords, open fifth or power chords, and 6/9 chords.

Exercises

Exercise 1: Description of Exercise

Exercise 2: Description of Exercise