Minor Harmony in Jazz Theory

MINOR HARMONY

It is possible to build diatonic chords on each degree of any of the modes, as with the major scale:

ex 6a: Dorian mode diatonic harmony

You will remember from Modes that the Dorian, Phrygian and Aeolian modes are minor, i.e. the interval between the root and 3rd degree is a minor third, hence the chord based on the 1st degree of the scale is a minor chord.

The Aeolian mode (sometimes called the natural minor) can be equated with the harmonic minor scale. Note that in this mode the chords on I, IV and V are all minor. (Ex: 6c)

ex 6c: Aeolian

The difference between the Aeolian and harmonic minor is that the 7th degree of the harmonic minor is raised a semitone to provide a leading note, i.e. a semitone leading from the 7th to 8th degree of the scale, which supplies a satisfying perfect cadence:

ex 6d: Aeolian and harmonic minor cadences showing the raised leading note.

We can see in ex 6d how the raised 7th in the harmonic minor allows for a conventional V-I cadence, where the V chord is a dominant 7th rather than a minor 7th.

If the harmonic minor scale is used melodically the augmented second interval between the 6th and 7th creates an exotic middle eastern flavour.

This is not the case with the melodic minor as it also has a raised 6th which makes it a closer relation to the Dorian mode. (ex 6e). In jazz this form of the melodic minor is used both ascending and descending.

ex 6e: Dorian and melodic minor cadences.

To understand conventional (non modal) minor harmony we need to build chords on the harmonic and/or melodic minor scales as we did with the major scale in ex 1b.

Note that there are two possibilities for the root of the VI chord, depending on whether the harmonic or melodic scale is used.

Ex 6f: Variations in minor harmony

Apart from the fact that this is rather complex, we have an unsatisfactory situation here. The alterations to the 6th and 7th degrees of the scales were made for melodic not harmonic considerations. Using these scales to create chords is unsatisfactory in some cases, so in practice alternatives are borrowed from modal minor harmony, usually the Dorian or Aeolian:

1. Chord I. The major 7th is fine in some cases but the leading note is harmonically unnecessary and can sound slightly dissonant or too sophisticated for certain styles. It also clashes unpleasantly if there is a tonic in the melody. Other chords that can be used for chord I in a minor key are Im (triad), Im6 (from Dorian or melodic minor) or Im7 (from Dorian) - see ex 6h.
2. Chord II. The harmonic minor version (half diminished) is usually more satisfactory.
3. Chord III. The leading note (B natural) is ungainly and unnecessary as the chord is rarely if ever used as a cadential chord. A Bb (Dorian or Aeolian) is usually better.
4. Chord IV. Either chord is suitable. The minor 7th gives more of a minor flavour, but the dominant 7th on the IV is common, especially in latin jazz or jazz rock sequences with 2 chords repeated, e.g. Cmin7/F7/.
5. Chord V. Raised 7th is good as it allows for the conventional V7-I cadence.
6. Chord VI. Either chord can be used, depending on the preceding or following chords. The harmonic minor chord sounds more modal.
7. Chord VII. Could be either but the harmonic minor version (diminished) is more common. The VII chord is sometimes used as an alternative to a V chord and the diminished 7th makes a more satisfactory cadence in a minor key.

Although this appears more complex than major harmony it allows for a great deal of variety. To simplify we could use a combination of chords based on harmonic minor harmony with some borrowed modal chords.

ex 6g: Minor harmony with some borrowed modal chords.

As mentioned above there are several possibilties for tonic chords in a minor key (ex 6h).

ex 6h: Tonic minor chords. (Note that in a m6 chord the added 6th is always a major6th). In jazz earlier than the 60s a minor 7 is rarely used as a tonic minor and should be not be used (to avoid confusion with IIm7).

Melodic and stylistic considerations need to be taken into account when choosing which type of tonic minor chord to use. (Eg. m maj7 and m6 may sound too sophisticated or too old fashioned in some styles). When using RN analysis a minor triad, m6 or m maj7often indicate a minor tonic, - useful for locating new key centres. (m6 or minor triad could be chord IV, of a minor key, but if so this will be obvious by the presence of a minor tonic nearby)

It is important to show which root the VI and VII chords are based on when doing an RN analysis in a minor key:

Chord	RN
VI chord whose root is a minor sixth above the tonic	bVI
VI chord whose root is a major sixth above the tonic	VI
VII chord whose root is a minor seventh above the tonic	bVII
VII chord whose root is a major seventh above the tonic	VII