Diminished Chord Triads / Music Theory Lesson

Author: sleepfreaks

Understanding the Unique Sounding Diminish Chord

We previously took a look at how to construct major and minor chords.
This time, we will be taking a look at diminished chords.

✴︎ There are times when “diminished” implies a 4 part harmony chord.
In this article, we will be looking at diminished chords as a triad (3 notes),
and will consider the 4 part chord as the diminished 7th chord.

First, lets take a listen to the sound.
The chord will play after the individual notes are played.

It sounds kind of eerie doesn’t it?
Diminished chords are often depicted as the following:


The most common way you may see it written is as

  • C Diminished Chord = Cdim
  • D Diminished Chord = Ddim

Some of the depictions had a “-5” or “b5” on it.
It seems that the “5” may play a crucial role here.

Lets take a look on notation and the piano roll.



Above the root note C we can see an Eb and a Gb.
Next, lets take a look at the B diminished chord as well.

The chord will play after the individual notes are played.

These are the notes that make up the chord.



It only uses white keys, and is made very simple.
Now we know what notes make up a “C diminished chord” and a “B diminished chord”.

Lets compare the two chords side by side.
After selecting the B diminished chord, lets move the root up to C.


Now they have both become C diminished chords.

Similar to other chords up until this point, there is a rule when constructing diminished chords as well.
Lets see what notes are placed above the root to create a diminished chord.

Lets place intervals next to the C diminished chord and compare them.



With C as a root, lets extend the Eb and Gb above it to the right.


The intervals of a major chord were R, M3rd, and P5th.

When comparing a diminished chord to a major chord,



the M3rd has been lowered a half-step to a m3rd, and the P5th has been lowered a half-step to become a dim5th.
As mentioned in our article about intervals, when a interval named “perfect” is lowered by a half-step, it becomes a “diminished” interval.

Next lets compare it to a minor chord.
A minor chord was made up of the R, m3rd, and P5th (1,b3,5).



The m3rd remains the same, but the P5th has been lowered by a half-step to a dim5th.

Lets go further and take a look at the scale degrees as well.


  • Major Chord : R/M3rd/P5th
  • Diminished Chord : R/m3rd/dim5th
  • Major Chord : 1/3/5
  • Diminished Chord : 1/♭3/♭5

Last but not least, lets take a look at all the triad chords we’ve seen up until this point.


Though many other chords exist, we will conclude here for this article.

By learning all your major scales, you will be able to create major chords using the 1, 3, and 5 of each scale.
From there, by knowing the differences between chords, you can easily create other chords as well!

For example, try using D as a root to create a major chord,
minor chord, and diminished chord.


As you sequence/play notes and hear the pitches move around,
you can hear as the sound changes from bright, to dark, to eerie.

In our next article, we will begin looking at 4 part harmony chords.
Soon you will be able to compose your own songs!

Article Writer: Kazuma Itoh

講師 伊藤
After moving to the USA at 18 years of age with a scholarship from Berklee, he completed a 4 year study focused on song writing and arranging there.
Using this knowledge, he works across a variety of fields from pop music, film music, and more.