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Scale Theory II: Flat Nine and Minor/Major Seventh

Scale Theory II: the flat nine and minor/major seventh scales.
Now we have 2 more scales to look at. First of all the flat nine scale. We take C7 … and we add a note to it - not the ninth but the flattened ninth. If we were playing C7 on its own, just like this, and we want to include the flattened ninth then … we can include it. That’s the basic rooted chord.
The question is: what’s the scale that goes with it? It turns out that it’s a scale we’ve met before because it is a diminished scale, but it’s a diminished scale rooted on C sharp, not on C. The C sharp scale is … and if we root it on C … We know a diminished scale is a symmetrical scale and it goes tone, semitone, tone, semitone, tone, semitone, … but if we were to start it on the second note of the scale - in other words, treat it as a mode - then it would go semitone, tone, semitone, tone, semitone, tone, semitone, tone.
I see that scale as a mode of the diminished scale. Some people call it the “8 note scale” in that there’s 8 notes in the scale before you get back to the octave - 9 if you include the octave.
I like to think of it, as I say, as a mode of C sharp diminished where you start on C … The chords? We have the ninth voicing of C7 and we’re going to flatten the ninth - so we do that … Then the other one is where we take the thirteenth shape - the upper voicing - take the thirteenth shape. There isn’t a sixth in it - there isn’t a ninth in it - but we can add the ninth and we can flatten it - like that. You’ll notice that we’ve come across that chord before because that’s one of our ways of voicing a diminished chord or a diminished seventh.
It’s not surprising because we’ve got a diminished (scale) - namely C sharp diminished … So that’s the chord that we use. So that’s C7 flat 9 - where we flatten the ninth chord - and the flatten ninth scale. That’s going to enable us to do our II-V and then we get to I. What about I? There are some choices. Let’s think about I being in C minor. We’ve got the triadic sound of C minor without any seventh in. We can colour that by adding the ninth. It’s still basically just C minor, but maybe it’s got a ninth in as well.
We can add, as usual in jazz, the minor seventh to give us C minor7 and we can also use the chord where we use the major seventh or the natural seventh - that sound. And that’s known as the major minor seventh, because it’s got the major seventh in over a minor chord. Let me just give you an idea of its colour … When we have a II-V-I to a minor we can choose between a minor without a seventh, we could choose a minor with a flattened seventh and we can choose a minor with a natural seventh. Let’s choose a minor with a natural seventh. What’s the scale?
The scale is easy, in the sense that if we have the minor seventh … it’s the Dorian mode. If we naturalise the seventh … if we naturalise the seventh we get that … and I hope you recognise that as melodic minor ascending … if we do it with the melodic minor descending afterwards. In terms of the chords then we have - that’s the way we would play it. We could have a fifth if we want to. We could have a ninth if we want to, but the basic chord is like that - as opposed to C minor7 - C minor seventh - C minor with a natural seventh - a major seventh.
Sometimes people write C minor natural 7, but it’s not a frequently used notation. What about the voicings? Well we have the first inversion for C minor7 and all we do is naturalise the seventh … Similarly we have the third inversion and all we do is naturalise the seventh … So those are the scales that we need to look at. We’ve seen one is a mode of a diminished scale and the other is just the melodic minor ascending scale.

In our scale theory interlude we next look at the flat nine and minor/major seventh scales.

You can download the “Flat Nine Scale” and “Minor Major Seventh Scale” charts in PDF format at the bottom of this step.

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