Beginner's Guide To Diminished Chords | Part 1- What is a diminished chord?

Yash
Jun 12, 2022
5 min read

Updated: Oct 8, 2022

Diminished chords are often hand-waved away as "we'll look at these later" when learning about the diatonic chords of major scale.

So today, we are going to take a look at the theory behind this beautiful chord; How it's formed, where does it come from, it's variations. In Part 2, I will be talking about the creative uses of it.

You need to know what are intervals (like major 3rds, minor 3rds, etc.) to understand this article better, as well as how to make diatonic chords.

First encounter with diminished chord, and the symbol to denote it

When musicians just start learning about the concept of "diatonic chords" in music, the first example they take is the major scale. So let's start there.

A major scale has 7 notes, and when we start figuring out the diatonic chords in this scale, we see that the 1st, 4th and 5th chords are major, and 2nd, 3rd and 6th chords are minor.

But that leaves us with the 7th chord, which is neither major, not minor. To no one's surprise, considering the name of this article, it's a diminished chord. We use the degree sign "°" along with the chord root note to denote a diminished chord. E.g.- C°, E♭°, etc. In the roman numeral notation of chords, we use lower case roman numbers along with the diminished symbol. E.g.- ii°, vii°, ♭vi°.

So now we know that in a major scale, one of the diatonic chords is diminished, and it is the seventh chord, which makes it "vii°". Now let's take a look at how to form it.

How to make a diminished chord

A diminished chord is made up of two minor 3rd intervals stacked on top of each other. For example, let's take B°. It is the vii° chord in the key of C Major. The notes in this chord are B, D, F.

The interval between B and D is a minor 3rd, and the interval between D and F is also a minor 3rd.

The most interesting part about a diminished chord is the interval between the Root and the 5th of the chord. In this case, it would be B and F. If you count the half-steps (or semitones if you prefer) between them, you will notice that it is not a perfect 5th. It actually has 6 half-steps, which makes it a diminished 5th interval, giving the chord its name as well as hinting towards its function.

Try answering these questions to see if you are with me so far.

What are the notes in the C° chord?

We will make this chord by stacking minor 3rds. The chord will start on C, and a minor 3rd above that is E♭. Then, a minor 3rd above E♭ is G♭. Therefore, the chord notes are C, E♭, G♭.

What are the notes in A♭° Chord?

Following the same process as before: A minor 3rd above A♭ is C♭, and a minor 3rd above C♭ is E♭♭. So, the chord tones are A♭, C♭, E♭♭.

This is the simplest form of the diminished chord, which is a triad. But just like we have major 7 and minor 7 chords, we can also have diminished 7th chord. Let's see how that works.

Half-Diminished 7th chord

Let's continue to use the example of B° chord in the context of C Major scale. If we stack one more 3rd interval on the triad, we get the following notes: B, D, F, A.

Notice that this time, the interval between F and A is major 3rd. Therefore, this chord is not completely diminished.

We call it the half-diminished chord, or the "minor 7 flat 5 (m7♭5) chord".

The symbol to denote it is "ø". E.g.- Bø, F♯ø, A♭ø, etc. When we are using this symbol, it is understood that it is a half diminished 7th chord. You don't need to write "ø7"

Half diminished chord is diatonic to major scale. It is the viiø chord.

Another important thing to note here are the intervals of all the notes from the root of the chord. We have B to D, which is a minor 3rd. B to F, which is a diminished 5th, and B to A, which is a minor 7th (♭7).

Full-Diminished 7th chord

As seen earlier, the half-diminished chord contains a major 3rd interval on top of a diminished triad. But what if we just stacked another minor 3rd over a diminished triad instead? That is how we get the full-diminished chord.

In case of B°, we would get the notes B, D, F, A♭. Now this chord is only made up of stacked minor thirds. From the root, the intervals are minor 3rd, diminished 5th and diminished 7th (♭♭7).

We write a full-diminished chord using "°7". E.g.- B°7, G♭°7.

Full-diminished chords are NOT diatonic to the major scale.

Here are a few questions for you to test your understanding

What are the notes of Dø ?

This is a half diminished chord, so first let's just make the diminished triad. It would have a minor 3rd from D, giving us F. Then another minor 3rd from there gives us A♭. Then a Major 3rd from A♭ is C. Therefore, the notes are D, F, A♭, C.

What are the notes of F°7?

Let's solve this one by finding all the required from the root. We know that the notes of a full-diminished chord are Root, Minor 3rd, Diminished 5th and Diminished 7th.

Here, root is F. Minor 3rd is A♭. Diminished 5th from F is C♭. Diminished 7th from F might be a little trickier to figure out. You just need to flatten the minor 7th interval. (In other words, you are flattening the major 7th interval twice). Major 7th from F is E. Minor 7th would be E♭, and diminished 7th would be E♭♭.

Therefore, the notes of F°7 are F, A♭, C♭, E♭♭.

How many tritones are there in a half-diminished chord? How many in a full-diminished chord?

If you are not familiar with tritones, just remember that if two notes are 6 Half-Steps or 3 Whole Steps apart, they are forming a tritone.

In a half diminished chord, there is only one tritone, and that is between the root and the diminished 5th.

In full-diminished chord, there are two tritones. One of them is between the root and diminished 5th, the other one is between the minor 3rd and diminished 7th.

Which chord has the notes G, B♭, D♭, F?

Look at the intervals of all the notes from the root. G to B♭ is minor 3rd, G to D♭ is diminished 5th and G to F is minor 7th. Therefore, this is a Gø chord.

The symmetry of full-diminished chords

You need to know the concept of enharmonic equivalents to understand this part better.

We have seen how to make the full diminished chord, but it possesses a very interesting quality that makes it extremely flexible. That quality is its symmetry. Let's try to understand this symmetry by taking the B°7 chord.

The notes of B°7 are: B, D, F, A♭

The first inversion of this chord would be: D, F, A♭, B. Try to figure out the intervals in this chord. D to F is a minor 3rd, F to A♭ is a minor 3rd. A♭ to B is technically an augmented 2nd interval, but if I write B as C♭ (I can do this because they are enharmonic equivalents), A♭ to C♭ is again a minor 3rd. What does it mean? It means that the first inversion of a full-diminished chord gives us another full-diminished chord. In this case, we got D°7 on inverting B°7.

Let's invert it once more. The notes we get are: F A♭ C♭ D. This time we'll replace D with E♭♭ (again, enharmonic equivalents).

Now, let's check the intervals. F to A♭ is minor 3rd, A♭ to C♭ is minor 3rd and C♭ to E♭♭ is minor 3rd. This makes it F°7 chord.

Now, one last inversion. The notes are: A♭ C♭ E♭♭ F. Using enharmonic equivalents again, we get:

G♯ B D F. Here, again the intervals are stacked minor 3rds. Therefore, this is the G♯°7 (or A♭°7).

The conclusion is:

By inverting a full-diminished chord, we get another full-diminished chord.

Since there are 4 distinct notes in the chord, we can see that the 4 full-diminished chords formed on these notes are basically just one chord.

We know that there are 12 notes in an octave. 4 of those belong to one diminished chord, leaving us with 8 more. By applying some simple logic, we can conclude that we will get 2 more diminished chords from these 8 notes.

There are essentially only 3 full-diminished chords. Every other full-diminished chord is just an inversion of one of these three. The three groups are:

B°7, D°7, F°7, G♯°7
C°7, E♭°7, G♭°7, A°7
C♯°7, E°7, G°7, B♭°7

Conclusion

In this part, we learnt about what is a diminished chord, where it is found naturally, and how to make it.

Diminished triad is made up by stacking two minor 3rd intervals. It is the vii° chord in major scale. The notes in it are root, minor 3rd and diminished 5th.

Half-diminished chord is made up by adding a major 3rd interval over a diminished triad. The notes in it are root, minor 3rd, diminished 5th, minor 7th. It is diatonic to major scale (viiø)

Full-diminished chord is made up by stacking three minor 3rds. In other words, by adding another minor 3rd on top of a diminished triad. The notes in it are root, minor 3rd, diminished 5th, diminished 7th. It is NOT diatonic to major scale.

In Part 2, I will explain general uses of diminished chords and how you can use it to enhance your compositions.

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