Four Diminished Chords You Can Form From The Octatonic Scale

In this lesson, I will be showing you four diminished chords you can form from the octatonic scale.

Although the octatonic scale is not one of the traditional scales we covered previously, you can use it in the formation of diminished chords. Diminished chords are important in music for a variety of reasons that we won’t go into in this lesson.

Let’s get started with our lesson today, by doing a review on the octatonic scale.

A Short Note On The Octatonic Scale

The term octatonic refers to a class of scale that consists of eight notes. Therefore, the term octatonic can be broken down into: ‘oct’ and ‘tonic’.

Oct means eight while tonic means tone. If you put that together, the octatonic scale simply means an eight tone scale.

Formation Of The Octatonic Scale

Although there are so many perspectives to the formation of the octatonic scale, I’ll be showing you the conventional formation of the octatonic scale by alternating between whole steps and half steps.

A scale is a regular succession of notes in ascending or descending order.

We’ll be doing a regular succession of notes in ascending or descending order using half steps and whole steps.

Starting from C:

…we’ll be alternating whole steps and half steps until its octave:

Here is how it works…

From C:

…a whole step from C is D:

…a half step from D is D#:

…a whole step from D# is F:

…a half step from F is F#:

…a whole step from F# is G#:

…a half step from G# is A:

…a whole step from A is B:

…and a half step from B takes us back to C:

Altogether, this is the C octatonic scale:

…which is known as the octatonic whole-half scale.

Attention: There’s another octatonic scale (but that is not our focus in this lesson) that can be form by an alternation of half steps and whole steps. This variant of the octatonic scale known as the octatonic half whole.

Our focus in this lesson is the octatonic whole-half scale, which is formed by alternating whole steps and half steps.

“Let Me Also Add This Alternate Formation Technique…”

The octatonic scale can also be formed by the superimposition of two diminished seventh chords that are a whole step apart. For example, to form the C octatonic whole half scale:

…we can superimpose two diminished seventh chords that are whole steps apart.

Here’s how it works…

The C diminished seventh chord:

…and the D diminished seventh chord:

…if superimposed in one octave:

…produces the C octatonic whole-half scale.

That’s the much we can take on the octatonic scale. Here’s the octatonic scale in all twelve keys…

C octatonic whole half:

C# octatonic whole half:

D octatonic whole half:

Eb octatonic whole half:

E octatonic whole half:

F octatonic whole half:

Gb octatonic whole half:

G octatonic whole half:

Ab octatonic whole half:

A octatonic whole half:

Bb octatonic whole half:

B octatonic whole half:

Now that we’ve covered the octatonic scale, let’s get into the formation of diminished chords using the octatonic scale. But before we do that, what are these diminished chords? 

“What Are Diminished Chords?”

Although there are two qualities of chords – if we’re classifying chords according to tonality, that is – major and minor chords, however, there are special classes of chords that even though they are minor chords, they contain diminished intervals.

Consequently, they are known as diminished chords. Diminished chords are basically chords that contain diminished intervals.

There are various classes of chords – triads, seventh chords, ninth chords, eleventh chords, and thirteenth chords. In the same vein, there are also various classes of diminished chords, which are not limited to…

• Diminished triads
• Diminished sevenths
• Diminished major sevenths
• Diminished major ninths

Let’s explore these classes of diminished chords.

The C diminished triad – C, Eb, and Gb:

The intervallic constituents of the C diminished triad are C-Eb:

…which is a minor third interval,

…and C-Gb:

…which is a diminished fifth interval.

It is the diminished fifth interval in the diminished triad that makes the diminished triad a diminished chord.

The C diminished seventh chord which consists of C, Eb, Gb, and Bbb is spelled as C, Eb, Gb, and A:

…for the sake of simplicity. The C diminished seventh chord:

…consists of the following intervallic constituents…

C-Eb:

…a minor third interval.

C-Gb:

…a diminished fifth interval.

C-Bbb (which we are substituting with A):

…a diminished seventh interval.

So it is these two diminished intervallic constituents (the diminished fifth and diminished seventh intervals) that give the diminished seventh chord its diminished quality.

There’s another class of diminished chords known as the diminished major seventh  chord, which is practically a diminished triad with a major seventh interval. The C diminished major seventh:

…can be broken down into the C diminished triad:

…and another note that is a major seventh above the root of the C diminished triad. A major seventh interval above C is B:

Addition of B:

…to the C diminished triad:

…produces the C diminished major seventh chord:

“…and one more class of diminished chords!”

The fourth class of diminished chords are the diminished major ninth chords. The diminished major ninth is an extension of the diminished major seventh chord. Adding D (which is the ninth interval):

…to the C diminished major seventh chord:

…produces the C diminished major ninth chord:

Attention: Ninth intervals can be associated with the second tone of the scale. Due to the fact that C-D:

…is a major second, the transposition of D:

…to its higher octave:

…produces the ninth interval:

It is the addition of this ninth tone to the basic diminished major seventh chord that formed the diminished major ninth chord.

Final Words

In another lesson, we’ll be looking at these diminished chords and how they can be formed from the octatonic scale.

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Chuku Onyemachi

Head of Education at HearandPlay Music Group

Onyemachi "Onye" Chuku is a Nigerian musicologist, pianist, and author. Inspired by his role model (Jermaine Griggs) who has become his mentor, what he started off as teaching musicians in his Aba-Nigeria neighborhood in April 2005 eventually morphed into an international career that has helped hundreds of thousands of musicians all around the world. Onye lives in Dubai and is currently the Head of Education at HearandPlay Music Group and the music consultant of the Gospel Music Training Center, all in California, USA.

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