Interesting question from Matthias @lieu512927 on Minor Chords… I think others may benefit from this great question so I am reposting in the forum.
Are the extensions of minor chords also coming from the major scale or do I have to look at one of the three minor scales? For example: The 13th of the C natural minor scale would be an Ab but the 13th of a C major scale would be an a. So when there is a Cmin13 chord on the lead sheet where does the 13th come from?
To answer this question let’s discuss a little modal theory:
Firstly, yes you are correct that the Natural Minor Scale has the b13.
The most common choice of scale to play over minor chords is the Dorian mode. The Dorian mode is the major scale with the b3 and b7. The “Melodic Minor Mode” or “Jazz Minor Scale” is also a nice ‘colour’ because it has major 7th, I look at this as the major scale with a b3.
I always try to relate everything back to the major scale. The natural minor scale is in fact the major scale… they contain the same notes, just starting on different scale degrees.
Most often, when working from lead sheets, the melody note over minor chords will be from the Dorian Mode. If the major 7th is in the melody, then the Melodic Minor Mode or Jazz Minor Scale, is being implied.
It is still possible to find the the b6 in the melody on a lead sheet - which is in both the Harmonic Minor and the Natural Minor scales - but this is not as common as the natural 6/13.
Choosing A Specific Minor “Colour”
The purpose of the harmonic minor scale, is to create more interesting harmonic possibilities in minor keys. That being said, the Harmonic Minor can be used to improvise over minor 251s to get some nice ‘colours’.
Whenever you play a minor chord, you can choose these different scales or ‘colours’ to add into the chord, or play over the top.
Each minor scale has a specific ‘colour’ which you should be able to hear and distinguish. The Dorian is very smooth and hip sounding. The Melodic Minor has a smooth and slightly mysterious sound from the major 7th. The Harmonic Minor sounds quite angular at the top with the minor 3rd interval that is created between the b6 and major 7, and also has an interesting middle-eastern flavour.
When you see the natural 6/13 on a lead sheet, the tune, or the composer, is likely asking for one of these specific ‘colours’ (Probably Dorian, or perhaps Melodic Minor). So that’s where I would say it comes from.
Does that make sense?
Kind of tricky to explain, but I think that should help. Let me know if you have further questions and I will happy elaborate further.