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.
The diminished triad
To better understand how to build a diminished triad, let’s consider a C major triad:
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:
The chord formula is 1-3-5.
Now, let’s build a C minor triad:
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!