The Diminished Scale

In this page we're going to discuss a common jazz scale called the the Octatonic scale.
In classic music any music scale that contains eight notes is called an Octatonic scale.
In jazz music however the term Octatonic scale is related to the diminished scale (since the scale is built out of two interlocking diminished seven chords which I'll show you later).

The Octatonic scale is ascending in a sequence of a whole step and a half step alternatively.

Since the scale is symmetric there only three different Octatonic scales. The root of the scale you're playing depends on which note set as the root.

This jazz scale has two modes actually. You can improvise with it starting with a whole tone - half tone or vice verse (half tone - whole tone).
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Let's see which chords are created by this jazz scale.

As you can see the Octatonic scale creates two interlocking seventh chords and this is why we name it so.

Therefore we'll use the scale when we would like to improvise on diminished chord.

In a II-V-I progression when the V is having a b9 we actually borrow the fifth from the Octatonic scale so we could naturally use the scale over this chord.

Same applies for a secondary dominant with a b9 (Click here to learn about the secondary dominant chord).



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The half diminished scale is taken from the Octatonic jazz scale as well.
Here's an example of how you might the scale to improvise with it over this jazz chord.

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