The next two examples demonstrate the difference between chords built from the natural minor scale and chords built from the harmonic minor scale. Fig. 3 shows the A natural minor scale (Aeolian) harmonized to get these common chords: Am, Bm7b5, C, Dm, Em, F, and G.
On the other hand, when you harmonize the A harmonic minor (Fig. 4), you get: Am, Bdim, Caug, Dm, E, F, and G#dim. Check it out: The B is now fully diminished, the C major has become C augmented (this is very unusual), the E minor has become E major, and the G major has become G#dim, another radical change.
It is also worth noting that you get two additional chords from the diminished chords: The notes in Bdim and Gdim are the same as the notes in Fdim and Ddim. How cool is that!
And there’s more: You can think of Caug as also being Eaug or G#aug. Trust me, this becomes a very cool concept when composing chord progressions. Oddly enough, very few contemporary, non-classical composers have taken advantage of this. The A section of “East St. Louis Toodle-Oo” by Duke Ellington and James “Bubber” Miley—later recorded by Steely Dan on Pretzel Logic—is one of the few tunes I know of that exploits the full potential of the harmonic minor sound.
Fig. 5 provides an approximation of this A section. Note the clever chord inversions—Am/C, Am/E, E7/B, and the diminished chords.
The last group of examples are various short harmonic minor modal vamps—most of them arpeggiated—to get you used to these new, unusual sounds. I’ve written out the various chord changes and arpeggios you’ll hear in the audio examples. After establishing the vamp for a few measures, I add melodies in various styles that will allow you to hear a few of the soloing possibilities these progressions suggest.
All the notes I play in these solos come directly from the harmonic minor scale, but that really isn’t the point. Instead, the point is the chord progressions all come from the harmonic minor scale and that allows us to play very simple solos, yet still evoke more exotic sounds and moods because of the nature of the chord progressions themselves.
The vamp in Fig. 6 provides a dark and tense atmosphere—perfect for an intro to a metal tune. Generally, here I think of B Locrian with a natural 6.