Today we will learn about the diminished chord, which is extremely used in pop music, jazz, electronic music, and much more. You will see that it’s very easy to build a diminished chord – again, it’s all about intervals.

There are three types of diminished chords: the diminished triad, the diminished 7th chord and the half-diminished 7th chord.

To better understand how to build a diminished triad, let’s consider a C major triad:

C

Any major triad consists of a root, a major 3rd and a perfect 5th. So, there’s a major 3rd between C and E and a perfect 5th between C and G:

C

The chord formula is 1-3-5.

Now, let’s build a C minor triad:

Cm

Notice that the difference between a major and a minor triad is the 3rd: it is a major 3rd on major triads and it is a minor 3rd on minor triads.

The chord formula for minor triads is 1-b3-5.

Finally, here’s a C diminished triad:

Cdim (or Cmb5, or even Co)

Notice that now we have not only the minor 3rd but also the diminished 5th.

The chord formula for diminished triads is 1-b3-b5.

So, if you want to build a diminished triad, take a major triad and lower both 3rd and 5th by one semitone.

Here’s another example:

Fdim (Fmb5 or Fo)

All diminished chords sound a lot dissonant, and its harmonic function is similar to the dominant 7th chord (we’ll cover that in a future lesson).

The half-diminished 7th chord

All you need to do to build a half-diminished 7th chord is to add a minor 7th to the diminished triad. Observe:

Cø7 (or Cm7/(b5))

The minor 7th can be quickly found by just lowering the root (or octave) one whole step.

The chord formula is 1-b3-b5-b7.

We can say that a half-diminished 7th chord is a diminished triad with a minor 7th.

The diminished 7th chord

The diminished 7th chord is a diminished triad plus a diminished 7th. Observe:

Co7 (or Cdim7)

Notice that we can build a diminished 7th by lowering the minor 7th a half step.

In interval theory, whenever you lower (by a half step) a major interval, it becomes a minor one. Whenever you lower a minor interval, it becomes a diminished one.

The chord formula for a diminished 7th chord is 1-b3-b5-bb7.

Let’s see another example:

Fø7 (or Fm7/(b5))

The diminished 7th chord can also be viewed as four notes all stacked in intervals of a minor 3rd.

That’s it! Keep practicing!

Good productions!