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I'm writing questions on index cards to help me study music theory. Some of the questions I make up, including this one: "What minor scale is the jazz chord C–7 associated with?"

I believe the answer is: the Dorian mode of C major. Hence, there is no minor scale associated with it. So I'm posting here to confirm that this is correct.

Is it true that a minor chord isn't always associated with one of the three typical minor scales (namely: natural minor, harmonic minor or melodic minor)?

  • Doesn't the Dorian mode of C major contain all the notes of C major? Usually called D Dorian. Maybe it should be the Dorian mode of Bb? It's the thorny one of C Dorian is not the same as the Dorian of C. – Tim Aug 7 '17 at 5:31
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To your question, in almost all cases involving traditional jazz harmony, a minor chord will be associated with one of the minor scales. However, there are four (not three) minor scales, and dorian is generally considered to be one of them. The four types are:

  • dorian minor
  • aeolian minor
  • melodic minor
  • harmonic minor

You'll notice natural minor isn't in the list. That's because aeolian minor and natural minor are identical (they both use a ♭6 and a ♭7).

The chord Cmin7 or C–7 does not definitively pair with any one minor scale. When you see this chord, here are the candidate minor scales:

  • C dorian minor
  • C aeolian minor

C melodic minor and C harmonic minor are not strong candidates, because both of those scales contain a natural 7th, which would contrast with the flat 7th of C–7. To determine which of the two viable candidates to use (dorian or aeolian), look at the key of the song or at the neighboring chords. For example, if the C–7 chord is contained in this progression:

| C–7 | F7 | BbMaj | BbMaj |

then C dorian minor would be more appropriate than C aeolian. The progression above is a ii-V-I in BbMaj, and it's possible to play over this entire progression only using modes of BbMaj. (In particular, you would play C dorian minor, then F mixolydian, and then Bb ionian.) It would be unconventional to play C aeolian minor in this progression, because the Ab contained in C aeolian would likely clash with the A♮ you would in F mixolydian.

By contrast, consider the tune All the Things you Are, which contains this progression:

| C–7 | F–7 | Bb7 | EbMaj7 |

Here, it is more conventional to play C aeolian than C dorian over the first measure. The reason is that the C–7 is leading to F–7, which contains an Ab. C aeolian also contains an Ab, and so it will lead nicely into the second measure.

To summarize, there are four types of minor scales, and only two of them would be natural choices for a C–7 chord. Determining which of the two candidates requires an evaluation of surrounding chords and/or the key signature. These two things will tend to favor one of the candidate scales over the other. So the answer to your flashcard question is this: "the jazz chord C–7 is associated with either C dorian minor or C aeolian/natural minor."

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    What about Phrygian? With a minor third doesn't it qualify at all? In some sequences, most if not all the notes would work, wouldn't they? +1 again! – Tim Aug 7 '17 at 5:27

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