Non-Diatonic Chords

This is a preview of the educational program A Jazz Improvisation Almanac which is under development for the Outside Shore Music Online School. Feel free to browse this preview and learn what you can from it. For a more completed product, though, check out the original freely browsable jazz textbook, A Jazz Improvisation Primer.

The section on function and resolution discussed only diatonic chords - ones that do not include any notes that are not part of the scale of the key. Music of any complexity will usually include non-diatonic chords as well, however. This provides additional harmonic color and richness. Most non-diatonic chords fall into a few general categories. Jazz musicians can benefit from an understanding of the function of non-diatonic chords because this can help suggest approaches for improvisation when such chords occur in a progression.

It has been observed that root movement upward by fourth is the strongest resolution in tonal music. Sometimes, to reinforce the resolution of a minor chord to the chord a fourth above, the first chord is altered to become a dominant seventh, even if this requires introducing accidentals. Such chords are called secondary dominants. For instance, here is a simple progression in which a minor chord resolves upward by fourth:

[EXAMPLE]

Here is that same progression with a secondary dominant:

[EXAMPLE]

These are among the most common non-diatonic chords in Western harmony. When analyzing secondary dominants, they may be notated in terms the root of the chord to which the chord resolves. For example, if a ii chord is made into a major chord in order to resolve to the V chord, the resultant chord is notated V/V:

[EXAMPLE]

It may also be notated simply as II7. Similarly, if a iii chord is made into a major chord in order to resolve to the vi chord, the resultant chord is notated V/vi.

Secondary dominant chords are very often seventh chords, as in the following example:

[EXAMPLE]

Just as the viio chord may substitute for the V7 chord, secondary dominant chords can similarly be replaced by diminished chords in this manner. For example, consider the following I-VI7-ii progression, which can also be notated I-V7/ii-ii:

[EXAMPLE]

The V7/ii chord can be replaced by the viio/ii:

[EXAMPLE]

Diminished chords used in this manner are called secondary diminished chords. They are often use to connect one chord to the chord a step higher, as in the above example. The majority of all diminished chords are used as substitutes for dominant seventh chords in this manner. Diminished chords may also be used in the reverse direction, however, particularly when the target chord is a minor chord:

[EXAMPLE]

These are known as passing diminished chords.

In classical harmony, there are a variety of chords known as augmented and neapolitan sixth chords that provide additional harmonic color. In jazz, these chords are generally seen as special cases of the tritone substitution. In a tritone substitution, a dominant seventh chord is replaced with the dominant seventh chord a tritone away:

[EXAMPLE]

When a dominant seventh chord in a V-I progression is replaced with a tritone substitution, the result is bII-I. The tritone substitution has the same third and seventh as the original, so the chords sound and resolve similarly:

[EXAMPLE]

Also, root movement upward by fourth is turned into root movement downward by half step, which is a stronger motion melodically. As will be seen in the section on altered chords, a tritone substitution can also seen as a combination of alterations to the original chord.

Another category of non-diatonic chords are chords borrowed from the parallel minor or major key - the minor or major scale built on the same root as the original. For example, minor key chord progressions often resolve to a major I chord. This is called a piccardy third:

[EXAMPLE]

Chord progressions in major keys often borrow chords from the parallel minor. In some cases, such as the iv chord, the root of the chord is diatonic to the original key:

[EXAMPLE]

In other cases, such as the bIII chord, the root of the chord is not diatonic to the original key:

[EXAMPLE]

Another common source of non-diatonic chords is the temporary modulation. A phrase may start out in one key but then temporarily change to another key. Temporary key changes may be to keys that are closely related on the circle of fifths, as in the following example:

[EXAMPLE]

Or they may be to keys that are more distantly related, as in the following example:

[EXAMPLE]

Another type of non-diatonic chord is the passing chord. This is a chord used between two other chords in order to lead from one to the other. Most often, this occurs between two chords a whole step apart, and the passing chord is built on the half step between these two chords:

[EXAMPLE]

Most non-diatonic chords in tonal music fall into one of the above categories. Chords that cannot be explained by conventional techniques are considered irregular. For instance, consider the following example:

[EXAMPLE]

The non-diatonic chord above does not fit into any of the previously discussed categories. While it is possible that there exists theory that can explain this usage, one can also simply accept it as irregular.

Copyright 2000 Outside Shore Music
Authored by Marc Sabatella

Non-Diatonic Chords