Harmonising the Minor Scale

So what happens if we want to harmonize the (harmonic) minor scale? Lets have a look (the harmonic minor scale is the basis for harmonies in a minor key). As an example we will use the A harmonic minor scale:

The first chord in this scale is (obviously) A minor, made up of the 1^st (A), the 3^rd (C) and the 5^th (E) notes of this scale. If we extend this to a 7^th chord we get A minor/major 7, since the 7^th is a major (sharp) 7^th (see ‘Four Part Harmonies’).

• The 2^nd chord (B) contains the 2^nd (B), 4^th (D) and 6^th (F) notes. This turns out to be a  diminished triad, B minorb5, since the 3^rd note (D) is a minor third and the 5^th note (F) is flattened.
  
  
• The 3^rd chord (C) contains the 3^rd (C), 5^th (E) and 7^th (G#) notes. We see that it is an augmented triad, since the 5^th (G#) is sharpened. So we end up with C aug (also denoted as C+). This chord is rarely used in minor harmonies because of it’s unusual sound.
  
  
• The 4^th chord (D) will contain the 4^th (D), 6^th (F) and 1^st (A) notes of the scale. This is a minor triad, so we get D minor.
  
  
• The 5^th chord (E) will be composed of the 5^th (E), 7^th (G#) and 2^nd (B) notes. This is a major triad, so we end up with E major.
  
  
• The 6^th chord (F) contains the 6^th (F), 1^st (A), and 3^rd (C) notes. This contains a major third so we get F major.
  
  
• The 7^th chord (G#) contains the 7^th (G#), 2^nd (B) and 4^th (D) notes. This is a diminished triad (minor third and flat 5^th), so we get G#minorb5.

Listen:

These chords are the same across all (harmonic) minor keys. So, in any (harmonic) minor key, we get the following chords:

The chord built on the 1^st note of the scale is MINOR
The chord built on the 2^nd note of the scale is DIMINISHED (minor^b5)
The chord built on the 3^rd note of the scale is AUGMENTED (relative major)
The chord built on the 4^th note of the scale is MINOR
The chord built on the 5^th note of the scale is MAJOR (dominant)
The chord built on the 6^th note of the scale is MAJOR
The chord built on the 7^th note of the scale is DIMINISHED (minor^b5)

You will notice this produces quite a few ‘non-standard’ (augmented and diminished) chords. For this reason, songs in a minor key will not only take chords from the harmonized harmonic minor scale, but also from the harmonized melodic minor and harmonized natural minor scales as well.

As an exercise, write out the melodic minor and natural minor scales, and harmonize these in the same way. You will find a different group of chords to use in addition to the above. This gives us a wide variety of chords to use when playing in a minor key.