Lesson 5 - Diatonic chord substitutions

In lesson 1, we saw how the diatonic seventh chord was the basic unit of jazz harmony. This chord can be expanded to five and six note chords without affecting its basic function or can be substituted with four and five note chords which are not seventh chords but function in like manner. The important fact is that these chord substitutions have identical function and can be used instead of diatonic seventh chords to add color to basic jazz sounds.

The I and IV chords
In lesson 1 we saw that the I and IV chords are major sevenths. However, the sixth chord (1-3-5-6) is also used as a I or IV chord. Also, the major seventh chord can be expanded to a five-note chord by using the major ninth (1-3-5-7-9). (Note: if necessary, the fifth can be omitted). The sixth chord is expanded to a five-note chord called the 6/9 chord (1-3-5-6-9). These chords can be expanded further by adding the 11th and 13th scale tones. In these further extensions incomplete chords are acceptable. The major eleventh (1-3-5-7-9-11) is often played (1-3-5-7-11) or (1-3-7-11). The major thirteenth (1-3-5-7-9-11-13) usually shows up as (1-3-5-7-13). These abbreviated chords can be considered as major sevenths with added diatonic tensions; i.e. Δ(9), Δ(11), or Δ(13).

The major six-nine is very commonly used as a progressive substitute for a sixth chord. The major ninth chord is seen frequently while the major thirteen is less common and the major eleventh is rare. The eleventh and thirteenth scale tones are found more commonly on dominant seventh chords.

Basic triads with added 9ths, 11ths, or 13ths are sometimes used. They give a very open sound which is being used by some of the more progressive composers. The addition of a thirteenth is equivalent to a sixth an octave higher and constitutes an open voicing of a sixth chord. The addition of an eleventh is usually considered a suspended fourth although the fourth is an octave higher. The addition of a ninth is called an add9 chord (1-3-5-9) and is sometimes written C(9).

The VII chord
The Ø is rarely seen in larger extensions. The ninth of this chord must be a flatted ninth to be diatonic and the Øb9 is a pretty wild sound. Theoretically, this chord can be extended to become a ninth, eleventh, or thirteenth chord. Possibly, these chords will become acceptable in the future with further advances in jazz.

The V chord
The V7 chord is almost always found in an expanded form. The dominant seventh chord is considered by most jazz players to have an uninteresting dullness. The ninth chord (1-3-5-b7-9) or thirteenth (1-3-5-b7-9-11-13) chords are used more often as a V chord in major keys than the standard dominant seventh. The dominant ninth and thirteenth give a smoother, jazz-flavored sound than the dominant seventh.

The other standard diatonic substitutions for dominant sevenths are the 7sus4 chord (1-4-5-b7) and the eleventh chord (1-3-5-b7-9-11). These chords have similar functions. Each has a fourth (or eleventh in the higher octave) which is suspended and needs resolution to the third (or tenth in the next octave). Consequently, the 7sus4 or eleventh chords are commonly found just before a dominant seventh which is the proper resolution for a suspended fourth; i.e. G7sus4 leads to G7 and G11 leads to G7. Modern composers are using the 7sus4 or eleventh and resolving them to the tonic for a more progressive sound. Some have gone so far as to use them as the tonic chord of a blues-type progression (one in which the dominant sevenths and their substitutes are the main chords) for a very unresolved sound full of tension and conflict.

In jazz, V chords are often seen with non-diatonic alterations which are borrowed from the minor key tonality. These non-diatonic alterations will be discussed later.

The II, III, and VI chords
The II, III, and VI chords are minor sevenths in basic jazz harmony. The II and VI expand easily to minor ninths (1-b3-5-b7-9), but the III chord must be a minor seventh with a flatted ninth (1-b3-5-b7-b9). As a result the III chord is usually not seen in any expansions but solely as a minor seventh chord.

The II and VI chords are seen as minor ninths and minor elevenths (1-b3-5-b7-9-11). The m7sus4 chord is often used as an abbreviated version of a minor eleventh. The minor thirteenth chord (1-b3-5-b7-9-11-13) is only available as an extension of the II chord.

Now that we have many new chord substitutions, the basic progressions in lesson 2 can be embellished and made into more modern sounds. Take the basic II-V-I in the key of C:

|Dm7	G7	|CΔ		|

It can become:

|Dm9	G13	|C6/9		|
or
|Dm7sus4 G9	|CΔ9		|
or
|Dm11	G7sus4	|CΔ13		|

The possibilities are endless. You can use these to punch up a dull progression or in composing modern jazz. Also, knowledge of the substitutions is a must in improvisation.

In improvisation you must work backwards, taking the extended chords and simplifying them to their diatonic seventh forms to find the key center. The progression:

|C6/9	Am11	|Dm9	G13	|

simplifies to:

|IΔ	VIm7	|IIm7	V7	|

in the key of C and requires a C major scale for improvising. The diatonic substitutions do not change the basic function of the chord and therefore the method for determining key centers is unchanged. However, first you must reduce the complex chords to a more manageable size.

Diatonic chord substitutions

Exercises

1. Play the following progressions.
2. Analyze each progression and determine key centers.
3. Practice soloing ever these chord sequences by using a tape recorder to make a rhythm track or have a friend play the progression while you solo.