4. Natural
Minor Mode Harmony
vs.
Borrowed Parallel Major Harmony
In true pure modal tonal centers, the chords tend to be triads or at
most 7th chords. The harmonic sequences are generally simple and repetitive.
The function of the "dominant chord" (the second most important chord
in the key) is to propel you into the Tonic. In major harmony, the chord
with the most forceful resolution to the tonic is built off the fifth
degree of the scale ("dominant
V").
In the case of the Dorian and Aeolian modal
harmony, the dominating cadential chord is built respectively off the
4th and b7th degrees.
Many
folk musics use pure Dorian or pure Aeolian progressions for their minor
songs.
The Harmonic Minor was invented to provide a leading
tone in order to give a stronger cadence than either the dorian IV->i
or aeolian bVII->i movements yield (via "borrowed parallel major
harmony").
Often
entire sections of a tune will use Aeolian and the only time the Harmonic
Minor comes into play is whenever a "dominant V chord" resolution is
needed.
Hence
the term "Harmonic" minor - it is an "artificial" creation designed
to aid the harmonic accompaniment.
The Harmonic Minor scale leaves some folks uneasy with the "big jump"
between the b6 and the #7. The Melodic Minor was invented to
smooth over the jump and be "more melodic". Hence the term "Melodic
Minor".
You'll note that the only difference between the Melodic
Minor and its parallel Major scale is that the Melodic Minor has a b3.
