Week 4: Diminished Triad + Chord Cheat Sheet

We’ll be focusing on the diminished chord in today’s lesson.

The diminished triad isn’t as common as the major and minor triads we’ve covered in past weeks and after this lesson, you’ll know exactly why.

Once again, welcome to lesson 4 of our 16-week chord revival program.

“Who can define the diminished triad?”

The word diminished literally means to make smaller.

The diminished triad is a minor triad with a smaller fifth (diminished fifth). It is this diminished fifth interval that influenced the name of this triad.

So if you make the fifth of all the minor triads we learned last week smaller by a semitone (to form a diminished fifth), this will produce a diminished triad.

For instance…

The C minor triad is formed by playing C, Eb, and G:

C is the first (aka – “root”):

Eb is the third:

G is the fifth:

If we make the fifth tone (G) smaller by lowering it to Gb:

…this will produce the C diminished triad:

…which literally means “a minor triad with a smaller fifth.”

The importance of the fifth chord tone in chord formation is that it determines the stability of a chord.

There’s only one fifth that is considered universally stable. It is called the perfect fifth. Triads that have a perfect fifth are stable while triads that have either raised or lowered fifths sound unstable and have the tendency to resolve to other chords.

This means that the lowering of the fifth chord tone to produce a diminished chord tampered with the stability of the chord. That’s why the quality didn’t change, only the stability.

It’s still a minor chord but with a flat five.

Now that we’ve provided a basic definition of the diminished triad, let’s delve into the intervallic components of the chord.

Intervallic Components Of The Diminished Triad

Every chord, no matter how big or complex, can be broken down into intervals (two notes). Triads are formed with three notes, therefore breaking them into intervals is a piece of cake.

Let’s look at the intervals that make up the diminished triad. We’ll use the C diminished triad:

…that we covered in the previous segment.

Below are the two intervals that make up the diminished triad:

C-Eb:

…which is a minor third.

C-Gb:

…a diminished fifth.

The intervals of the minor third and diminished fifth make up the diminished triad and familiarity with them will help you understand this chord in all 12 keys.

The Minor Third Interval

The minor third is the interval between the first and the third degree of the minor scale. For example, in the C minor scale:

…the interval between the first scale tone (C):

…and the third scale tone (Eb):

…is a minor third:

However, it’s easier to see it as a major third interval that is lowered by a semitone (half step). In the key of C major, a major third is:

…and this is because C and E are the first and the third degrees of the C major scale. If you lower C-E by a semitone (half step), this will produce:

…C-Eb, a minor third interval.

Knowledge of the minor third intervals in all keys means you’ve covered 50% of of the intervallic components of the diminished triad.

The Diminished Fifth Interval

The diminished fifth interval can be formed when we make the perfect fifth, which is the interval between the first and fifth degree of the minor or major scale, smaller by lowering it a semitone (half step). Using the C minor scale:

…the interval between the first scale tone (C):

…and the fifth scale tone (G):

…is a perfect fifth:

If the fifth tone (G):

…is lowered by a semitone:

…with the intention of making it smaller (i.e – diminishing it), this will produce a diminished fifth interval.

The diminished fifth interval is also known as the tritone, because it consists of three adjacent whole steps. There was a time when this interval was considered devilish and banned because of its extreme dissonance. (If this interests you, check out my post on the devil in music).

The diminished triad inherits its instability from the diminished fifth interval. If the diminished triad had a perfect fifth interval (which is considered to be universally consonant), it wouldn’t be unstable.

Pay attention to this…

If you change the quality of fifth (of the diminished triad) from a diminished fifth to a perfect fifth, you’ll end up reversing it to a minor triad. For example, C-Eb-Gb:

…is a diminished triad.

If you raise its fifth (which is Gb):

…by a semitone (half step), this will produce C-G:

…and C-G in turn will yield a minor triad:

Now that we’ve covered the intervallic components of a diminished triad, let’s look at the chord formation of diminished triad.

“How Can Diminished Triads Be Formed In All The Keys?”

There are many ways to approach chord formation of the diminished triad.

However, I’ll limit it to three approaches – scale, interval, and chord approaches.

Formation #1 – Scale Approach

The diminished triad can be formed from the octatonic scale. Octatonic scale literally means an eight-tone scale.

There are two known variations of the octatonic scale, octatonic whole-half:

…and octatonic half-whole:

Let’s look at the scale formation of the octatonic scale.

Octatonic Whole Half

Starting from C:

…a whole step will yield D:

…a half step will yield Eb:

…a whole step will yield F:

…a half steo will yield F#:

…a whole steo will yield G#:

…a half steo will yield A:

…a whole step will yield B:

…a half will yield C.

Here’s the C octatonic whole-half scale:

Octatonic Half-Whole

Starting from C:

…C + a half step:

…Db + a whole step:

…Eb + a half step step:

E + a whole step:

F# + a half step:

G + a whole step:

A + a half step:

Bb + a whole step:

This is how octatonic half-whole looks.

Octatonic scales are not traditional scales. Therefore, spelling guidelines do not apply to them. It’s possible to have both sharp and flat symbols in the octatonic scale.

Let’s get into chord formation of the diminished triad using the octatonic whole-half scale.

To form F diminished triad, you’ll need F octatonic whole-half scale:

From the scale above, form F diminished triad by:

Starting on F:

…skipping a note (G in this case).

Picking a note (Ab in this case):

…skipping a note (Bb in this case).

…and finally, picking B:

F-Ab-B may not be the proper spelling of F diminished, but the diminished triad is formed and that is the ultimate goal. The proper spelling of F diminished triad is F-Ab-Cb:

While the octatonic scale may prove helpful in terms of chord formation, you must watch out for misspellings as they are bound to occur with the use of flat and sharps in the same scale, coupled with omission and repetition of letter names.

Formation #2 – Interval Approach

It’s possible to form the diminished triad using the intervallic components we covered earlier.

The diminished triad has two intervallic components:

Minor third

Diminished fifth

…which I trust you’re now familiar with, considering that we covered them earlier.

From C:

…adding a minor third (3 half steps):

…and a diminished fifth (6 half steps):

…will produce a diminished triad:

Applying this same approach to chord formation from any note will produce the diminished triad.

Formation #3 – Chord Approach

You can form diminished chord if you’re familiar with minor triads.

Diminished triads are unstable minor triads. If you diminish the fifth tone of a minor triad, this will produce an unstable variant, known as the diminished triad.

(Remember that the stability of a chord is in its fifth.)

Here’s the C minor triad:

Diminishing its fifth from G:

to Gb:

…will produce a diminished triad:

…a C diminished triad.

If the fifth tone of the G minor triad:

…which is D:

…is lowered by a half step, this will produce:

…a G diminished triad.

Minor vs Diminished Triads

Below are minor triads and diminished triads in all keys.

C minor vs C diminished triads:

C# minor vs C# diminished triads:

…which can also spelled as Db minor and Db diminished triads.

D minor vs D diminished triads:

D# minor vs D# diminished triads:

…which can also spelled as Eb minor and Eb diminished triads.

E minor vs E diminished triads:

F minor vs F diminished triads:

F# minor vs F# diminished triads:

…which can also spelled as Gb minor and Gb diminished triads.

G minor vs G diminished triads:

G# minor vs G# diminished triads:

…which can also spelled as Ab minor and Ab diminished triads.

A minor vs A diminished triads:

A# minor vs A# diminished triads:

…which can also spelled as Bb minor and Bb diminished triads.

B minor vs B diminished triads:

Additional Formation Technique – Symmetry

The diminished triad is symmetrical.

Symmetrical triads are triads that can be divided into two equal intervals.

It’s true that the diminished triad is made up of the minor third and the diminished fifth. However, if we consider it from another perspective, you’ll see that C diminished:

…can be broken down to:

C-Eb:

…a minor third.

Eb-Gb:

…which is also a minor third.

This means that the diminished triad consists of two minor third intervals that are placed side by side. Therefore, putting two minor third intervals together will produce the diminished triad.

A minor third interval built on F:

…consists of F and Ab. If another minor third interval is formed from Ab, this will produce:

Put together, F Ab +Ab Cb will amount to:

And that’s an F diminished triad.

Below are two minor third intervals you can put together to produce diminished triads:

C and Eb minor third intervals:

C# and E minor third intervals:

D and F minor third intervals:

D# and F# minor third intervals:

E and G minor third intervals:

F and Ab minor third intervals:

F# and A minor third intervals:

G and Bb minor third intervals:

G# and B minor third intervals:

A and C minor third intervals:

A# and C# minor third intervals:

B and D minor third intervals:

Final Words

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P.S –

Don’t forget to claim your quick reference guide on diminished triads by Jermaine Griggs (our President and Founder) that covers all you need to know to play diminished triads in all the keys with the least effort.

And remember that in this reference guide, you’ll be given 126 exercises that will drill you to perfection. Don’t miss this free guide!

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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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