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Jazz Theory and Practice

Module 5 a, b, c

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

Other Harmonic Structures

B. Extensions: 9th, 11th and 13th chords

Jazz Theory and Practice

Harmonic extensions are notes added to the chord in the second octave

beyond the 7th. In our study of jazz harmony we can easily find labels

for all of these chords with added extensions, but in common

performance practice among jazz musicians there are often wide-ranging

differences between the theoretical chord definition, and the actual chord

that emerges in performance (written or improvised):

� In the large repertoire of sheet music and lead sheets the harmony is

typically from our previous study: almost entirely added-6th and 7th

chords. Many melodic lines, however, contain implied extensions. To

keep the notation simple a basic dominant-7th chord might be

suggested, but certain notes in the melody, especially notes of longer

duration or on a strong beat will become extensions. Over a C7

chord, for example, a D becomes a 9th, or an A becomes a 13th. (but

not an added-6th if the 7th is present!)

� Many performers will routinely add extensions to 7th chords whether

they are notated or not. This happens not only with the “harmony

providers” (keyboard or guitar), but good horn players will include

extensions within improvisations. The practice varies widely

according to style and taste, but extensions to the V7 chord (9, b9,

#9, 13) are very common, and a final I chord is often decorated with

virtually any combination of extensions. This practice is so

widespread that many arrangers assume that the performer will add to

the harmony; another practiced freedom in jazz interpretation!

� Although it would seem that the practice of extensions is about adding

notes to the chord, in fact subtracting notes is almost more important.

� ©2016 Peter J. Clements

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The subtraction happens in two ways: (1) often during performance

some notated extensions are omitted for practical reasons, and (2) an

extended chord is almost never “complete”: a 13th chord theoretically

contains 7 different notes, but in practice 5, 4, and even 3-note

voicings are typical. The voicing of extended chords is an essential

skill for a good jazz performer, especially pianists, guitarists, and

arrangers.

The 9th, 11th, and 13th are all extensions, and are often regarded as the

outer limits of the jazz harmonic language, at least for chords built of

thirds. This is tertian harmony; there are other basic harmonic

structures used in jazz (especially quartal harmony: chords built of 4ths).

Notice, in the following example, that once the 13th is added to the chord

all seven notes of the scale are represented. The next added third

beyond the 13th is the 15th, which is the root, so isn’t really an added note

at all; there is no 15th chord!

5b1

This example shows extensions to both the major 7th and the dominant

7th chords, and how they are identified. The 11th chord has been omitted:

with a major triad on the bottom the 11th is almost never used, because

the major 3rd combined with the 11th produces a strongly dissonant minor

9th interval. In both 13th chords shown the 11th would almost always be

omitted in the voicing.

These “towers of notes” are certainly intimidating, but, in fact, are almost

never played that way by a keyboard or guitar player. In the previous

section we encountered examples of 9th chords using rootless voicing;

similar reductions are applied to 11th and 13th chords. Voicing becomes a

major issue with extended chords; each extension has its own “rules”.

The 13th is actually a 6th above the root of the chord, and, in fact, all the

extensions can be regarded in a similar way: the 11th is a 4th above the

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root, and the 9th is a 2nd above the root. With reduced voicing, then, can

a 13th chord ever be the same as a chord with an added 6th? Look at the

following examples of chords with extensions, as compared with chords

that simply have an added note in the first octave:

1. 2nds and 9ths:

5b2

The “C2” chord (or C(sus 2))is unusual, and, without a third, could be

heard as either major or minor. All the rest are true 9th chords; notice

that the two “add 9” versions are missing a 7th, so the 9th is added to a

triad. The two 6/9 chords are very common, usually voiced in a reduced

form. In module 5a there were various examples of rootless voicings for

9th chords. Remember that 4-note versions usually look like common 7th

chords; for 3-note versions, the three “essential” notes are the 3rd, 7th,

and 9th. Look at the following examples:

5b3

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There are many instances in the above examples, especially among the

3-note voicings, where another label could easily be applied: the Dm9

looks like an Fmaj7, the Gm9 looks like a Bbmaj7, etc. Realize,

however, that other chord notes could be in other parts, especially in the

bass.

There are frequent examples where a composer/arranger might label a

chord as a 9th chord, but add other notes for colour, especially the 13th:

5b4

Because each chord contains a 7th, the extra note is a 13th, not an added 6th.

The final example is labelled as a Gmaj7, but contains both the 9th and the

13th! This is a typical contradiction between jazz theory and jazz practice.

These voicing examples are all taken from actual keyboard parts, either

written for a small jazz ensemble or a big band.

2. 4ths and 11ths:

5b5

Beginning with a major triad, virtually every chromatic note in the octave

can be added to the chord as part of an altered chord or extension,

except for one note: the Perfect 4th above the root. Sometimes the 4th is

called the “avoid note”; if it’s added to a major chord, or even just given

too much emphasis in an improvisation it really sounds wrong. Given the

right context, however, a 4th may be added to a triad, 7th, or 9th chord,

with the 3rd omitted. These chords will have “sus” added to the label; an

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abbreviation for suspension. In classical harmony the suspension is a

very common musical device. It’s always on a strong beat, and creates

tension because it temporarily replaces a chord note, then moves down

one step to the chord note to release the tension. The most common

suspension is the 4-3 suspension:

5b6

In jazz harmony the suspension sometimes resolves (moves down a step

to the 3rd of the chord), but just as frequently doesn’t resolve at all; in

this case it’s really an “added 4th”, not a suspension, but is always

labelled as “sus” in common practice, and the 3rd is almost never included

in a “sus” chord. (Is it major or minor?) As mentioned earlier, the true

11th (octave + P4th) is seldom used with a major chord where it clashes

with the 3rd an octave below. In the examples above the 11th is used

with a minor chord below, producing a major 9th against the 3rd of the

chord, a much “softer” dissonance than it would be with a major chord.

The next example shows the #11 used with various major chords,

producing that same “softer” major 9th against the 3rd below.

3. Sharp 11ths

5b7

The #11 is a common extension, and is almost always used with a major

chord. It does add a particular colour to the chord which is easily

recognized: the tritone (augmented 4th) against the root below. Full 11th

chords contain six different notes, so are almost never played that way.

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Look at the following examples; for either 11th or #11th chords the

essential notes are the 3rd, 7th, and 11th. For a simple “sus” chord the

root, 4th, and 5th are essential, but “sus” chords often appear with added

7ths and 9ths as well. In the first two #11 chords in the example below,

the #11 is spelled enharmonically.

5b8

4. 6ths and 13ths:

5b9

13th chords actually appear quite often, even in pieces with few

extensions where most of the harmony is 7th chords. This is true in 19th

century Classical music as well, where the V13 often appears as a

dramatic climax at the cadence. It can almost be assumed that,

whatever notes are omitted from the 13th chord, the 7th should always be

there; this clearly produces the “13th sound”, which is entirely different

from an added 6th chord. For the 13th chord the 7th and the 13th are

essential notes, as well as the 3rd to identify the chord as major or minor.

Here are some sample voicings for the 13th chord:

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5b10

There is much to be learned from studying these examples, all taken from

jazz ensemble keyboard parts. The first three examples include the

three essential notes as well as the root in the first example, the 9th in

example 2, and the flatted 9th in example 3. In example 4 the root is

added, and the 5th is added as well in example 5. Example 6 is unusual

because the 13th is now below the 7th, producing a dissonant minor

second. Examples 7 and 8 add the 11th for the first time, but it’s the #11

to avoid a strong clash with the 3rd. If the C were used here there would

be two major 7th/minor 2nd intervals in the chord. The final two

examples do introduce the natural 11th to the chord, but it’s disguised

with the sus label… which means the 3rd has been replaced…no clash!

In these examples, as well as previous ones in the lesson, there is a

common principle in all the various voicings: The extensions are never in

the bass; but always in the upper voices. This is only logical: the 11ths

need a root or third below; the 13th almost always has the 7th below.

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Something to listen to:

The Boy (or Girl) Next Door has two #11 chords in the melody of the first

phrase, setting the character for the piece. Find one of the several

versions by Frank Sinatra; some versions include the verse at the

beginning.

Chelsea Bridge by Billy Strayhorn also has prominent #11’s in the first

phrase, and other extended chords throughout the piece. Check out the

1961 recording by the Duke Ellington Orchestra.

Take the A Train by Duke Ellington. The famous piano introduction is

built around a D7(#11) chord, which returns in the tune. Look for the

Ellington version.

There are dozens of “contemporary” big band arrangements from the

past 10 years that feature the harmonic language of extensions and sus

chords. Check out Mossman’s Samba Kinda Mambo; there are several

good performances by high school and college bands.