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Jazz Theory and Practice

Module 5 a, b, c

Dim. 7th & 9th Chords; Extensions to the 13th;

Other Harmonic Structures

C. Other Harmonic Structures

As was shown in Module 5(b) there cannot be an extension beyond the

13th; at this point all seven notes of the scale have been used. Starting with the basic array of 7th, 9th, 11th, and 13th chords, an extended array is

produced with alterations in all combinations: flat or sharp 5th, flat 7th, 9th, and occasionally 13th

, sharp 9th, (but is it really? see (2) below) and sharp

11th. Certain alterations, such as sharp 7th or flat 11th are meaningless

(think about it!).

Although we have worked our way up to the 13th, there are still numerous other structures that are part of the jazz harmonic language, but

many of them, as we shall see, are simply alternative descriptions of chords we have already discovered. It’s almost impossible to cover all of them;

what follows is a collection of other harmonic structures that are most likely to be found:

(1) Flat 5th, sharp 5th. The minor-7th(¯5) chord (or half-diminished)

was introduced in Module 2(c). It falls into the natural minor scale, and is almost always used for II7 in the minor key. This chord can

also be “borrowed” in the major key (see below).

The b5 can also be used in the dominant-7th chord, sometimes

with 9th and 11th extensions as well. In all cases, the lowered 5th

has an obvious tendency to resolve downward. The following are all variations of the II V I progression:

©2015 Peter J. Clements

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5c1

Sharpening the 5th of a major triad produces the augmented triad

(symbol: +) which most often appears within a 7th or extended chord. The raised 5th almost always resolves up a half-step:

5c2

(2) The #9 chord. From Module 4C you may remember that the Blues

often fall between major and minor: melodic patterns drawn from minor pentatonic or blues scales are combined with chord patterns

of mostly major chords. When the flat 3rd of the scale is combined with the major tonic chord, or the flat 7th of the scale is combined

with the major V chord, the result is a chord with both a major and minor third. Voicing is very important: the major third is almost

always in the lower octave, and the minor third in the upper octave. This produces an interval of a Major 7th between them; if the minor

third is on the bottom the interval becomes a Minor 9th, which is

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much more dissonant. In practice the chord is always used with at

least a 7th added:

5c3

This dissonant sound really helps to define the blues character. Finding a

label for this dissonant chord with two thirds is a problem; logically it should

be a 7th chord with an added b10 (the additional flat 3rd of the chord, in the

next octave). By tradition, however, ¯10 is almost never used; the chord

label includes ≥9, even though the actual note could appear as either a raised

9th or a lowered 10th. Look at the following example:

5c4

In this example the C7(≥9) includes the root, 3rd, 7th, and the b 10th,

instead of the ≥9th. This voicing (with or without the root), is almost

always used for this chord; both major and minor thirds are needed to

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define the sound. The Db7(≥9) does contain the ≥9 (E natural), but the

seventh is written enharmonically: it should really be C¯. Such

enharmonic spellings are very common in extended chords. In the

Play/Sing exercises that follow you will find a 12-bar blues harmonized

entirely with #9 chords.

(3) The mysterious ALT chord. A similar sounding chord with both

major and minor thirds is a little more complicated than the 7(≥9)

chord; it typically contains the 7th, both the ≥9 and the b9, and the b13;

the 5th is almost never present, and ≥11 is optional. This could turn

into a very complex label; but in practice the label is simply “alt” (for

“altered”), and the label may include the 7th or not: “C alt” and “C7

alt” are used interchangeably. This all sounds very complicated, but

look at this example where the “alt” chord emerges in a very simple,

expressive context:

5c5

In this short excerpt, from the standard harmonization of A Child is

Born, the middle chord is labelled D7(¯9), which describes the chord on

the downbeat, but the remaining notes in the measure help define an

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“alt” chord, without the 5th and ≥11. The sound of the “alt” chord is

clearly there, because of the altered dominant cell (see figure 5c7).

This next example is taken from an actual jazz arrangement where the

“alt” chord serves as the final chord of the piece. The simplest way to

look at this “tower of notes” is to see it as two diminished-7th chords.

In the arrangement the C13 label is used, but if the 13th is lowered a

half step (3rd chord) it becomes a full “alt” chord. The difference in

sound between the 2nd and 3rd chords is hardly discernable.

5c6

As with other chord structures there is a scale that contains all the

notes of the “alt” chord, other than the 5th, which is seldom used. If

the first 4 notes of the diminished scale continue to the octave in

whole tones, the combined result is the diminished whole-tone scale.

One way to find the scale is to think of the root of the alt chord as the

7th step of a jazz melodic minor scale, and remember that a jazz

melodic minor scale is simply a major scale with a lowered third!

Look at the example below; here is the easiest way to find the

matching scale for D7alt:

(a) Start with an E¯ major scale; 7th step (D) to 7th step

(b) Make it melodic minor: Change GΩ to G¯

The bottom 4 notes are sometimes called the Altered dominant cell,

which we could add to our family of tetrachords from Module 1a.

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Notice that the major 3rd of the chord, and both versions of the 9th are

in that cell; this produces the essential character of the alt chord. The

top half of the scale: four whole-tones in succession form a Tritone

Tetrachord that was introduced in Module 1a.

5c7

(4) Voicing in 4ths; Quartal Harmony

We have shown that extensions to the 13th include every note of the

scale. Even though a complete 13th chord is seldom used, look at

different versions of the 13th chord, and notice how the character can

change, depending on the way the notes are arranged:

5c8

The first two examples are common 13th chords, with #11 added. Notice

that the notes are identical, but the second version uses a polychord

label. The third version uses a different polychord label that clearly

describes a different voicing, without #11. The last three versions all

feature 4ths (both perfect and augmented 4ths) in the voicing. A chord

that is built of 4ths, rather than 3rds, has a more open, slightly more

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dissonant sound, and an arranger often uses that voicing quite

deliberately to “colour” the harmony. We have seen many quartal

voicings in previous sections; here are a few examples of chords using

quartal voicings, all taken from actual keyboard parts for jazz ensemble:

5c9

All of these examples are rootless voicings, and in all cases there are

other notes sounding at the same time (bass, horn parts, etc.) so the fact

that the written chord seems to have little to do with the chord symbol

shouldn’t be surprising. The first and third examples are the same but for

one note, but have quite different labels. The fifth example contains no

black notes, and really looks like an F major 9th chord. The quartal

voicings are especially effective for brass ensembles.

(5) “Slash” chords and polychords

“Slash” chords are nothing more than a chord with a specified bass note,

and will be covered in more detail in Module 6. They are mentioned

here, together with polychords, because the two are sometimes confused

with one another, and the labelling is sometimes interchanged by

arrangers and composers. The most common convention is that a

“slash” chord, with a sloped line, indicates a single bass note for the

chord, and a polychord, with two chord symbols separated by a horizontal

line, indicates two different simultaneous chords:

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5c10

Unfortunately, the labelling is not always consistent, and sometimes the

performer must guess as to whether the label indicates a polychord or

not.

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The most intriguing aspect of polychords is that, once in the region of

harmonic extensions to the 13th, almost every polychord will have an

alternate label as a single extended chord. Remember that a full 13th

chord contains every note in the scale; once chromatic modifications are

added, the possibilities are almost endless. Look at the following

examples, with alternate labels:

5c11

These are somewhat simpler structures than the examples from the

previous illustration (5c10). The chords in the bass clef (dominant 7th,

minor 7th, major 7th, all with the 5th omitted) are sometimes referred to

as a “shell voicing”, set against various triads in the treble clef. The 5th is

omitted to “open up” the voicing, and also, in many cases, to avoid a

clash with #11.

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Polychords can be a combination of virtually any two chords, and either

or both chords can be triads, 7th chords, or extended chords; the

combinations are endless! Long before they became a part of the jazz

language polychords were used extensively in late 19th- and early 20th-

century classical music. One of the well-known examples, from a

hundred years ago, is the “Petroushka chord” used by Stravinsky: a C

major and F# major triad together (tritone substitutes!).

Something to listen to:

Blue Train by John Coltrane is coloured by #9 chords throughout.

A Child is Born by Thad Jones is a wonderful jazz ballad in triple time.

(“alt” chord example appeared in the lesson)

In at least one lead sheet for Neil Hefti’s Cute, and A7(alt) chord is used

as part of the turnaround, leading to both the first and second phrases.

In Jobim’s Desfinado listen for a dominant-7th with ¯5 in the 3rd and 4th

measures, answered by a minor-7th with ¯5 in the 7th and 8th measures.

A Ghost of a Chance uses a dominant 7th with #5 in both the main theme

(2nd bar) and in the 2nd bar of the bridge as well. (a “ghostly” sound?)

Miles Davis’ Blue in Green uses a dominant 7th with both #5 and #9, first

in the 2nd bar, then in two other places.

Return to the menu, and try the PLAY/SING and WRITE exercises for Module

5c.