Diminished Chords
Diminished chords create tension, movement, and that unmistakable “something is about to happen” sound. They may look complicated on paper, but the basic shape is surprisingly simple.
How Do You Play a Diminished Chord?
Start with a normal major triad. Lower both the 3rd and the 5th by one half step.
Diminished Chord Theory
A diminished triad is built by stacking two minor 3rds.
C → E♭
Minor 3rd (m3)
E♭ → G♭
Minor 3rd (m3)
You can also measure the notes from the root:
C → E♭
Minor 3rd (♭3)
C → G♭
Diminished 5th (♭5)
What's With All the Weird Flats?
Diminished chords sometimes produce strange-looking note names such as F♭ or even A𝄫.
Don't panic. The reason is actually pretty simple.
Chords are normally spelled using every other letter of the musical alphabet. So if the root is D, the chord needs some kind of D – F – A.
On the piano, F♭ is the same key as E, and A𝄫 is the same key as G.
When Do You Use Diminished Chords?
Diminished chords are excellent passing chords. They create tension that pulls your ear toward the chord that comes next.
Try this progression:
Notice how strongly the C♯ diminished chord wants to resolve into D minor.
Three Diminished Chord Types
Once you understand the basic diminished triad, you'll commonly see three related chord types.
Half-Diminished 7th Chords
To create a half-diminished 7th chord, start with a diminished triad and add a minor 7th.
C → E♭
Minor 3rd
C → G♭
Diminished 5th
C → B♭
Minor 7th
Symbol
Cm7(♭5) or Cø7
Fully Diminished 7th Chords
A fully diminished 7th chord stacks one more minor 3rd on top of the diminished triad.
On the keyboard, B𝄫 is the same piano key as A. But theoretically it is called B double-flat because it functions as the diminished 7th above C.
C → E♭
Minor 3rd
E♭ → G♭
Minor 3rd
G♭ → B𝄫
Minor 3rd
Stacked Formula
m3 + m3 + m3
Fun Fact: One Shape, Four Chord Names
Fully diminished 7th chords are perfectly symmetrical. Every note is a minor 3rd apart.
Because of that, the same four piano keys can represent four different diminished 7th chords depending on which note you treat as the root.
They can function as versions of C°7, E♭°7, G♭°7, or A°7.
Same four piano keys. Different root. Different chord name. Pretty cool!
All Diminished Triads
Use this chart as a quick reference. The formula is always 1 – ♭3 – ♭5.
| Chord | Root | ♭3 | ♭5 |
|---|---|---|---|
| Cdim | C | E♭ | G♭ |
| C♯dim | C♯ | E | G |
| Ddim | D | F | A♭ |
| E♭dim | E♭ | G♭ | B𝄫 (A) |
| Edim | E | G | B♭ |
| Fdim | F | A♭ | C♭ (B) |
| F♯dim | F♯ | A | C |
| Gdim | G | B♭ | D♭ |
| A♭dim | A♭ | C♭ (B) | E𝄫 (D) |
| Adim | A | C | E♭ |
| B♭dim | B♭ | D♭ | F♭ (E) |
| Bdim | B | D | F |
All Fully Diminished 7th Chords
The fully diminished 7th formula is 1 – ♭3 – ♭5 – 𝄫7.
| Chord | Root | ♭3 | ♭5 | 𝄫7 |
|---|---|---|---|---|
| C°7 | C | E♭ | G♭ | B𝄫 (A) |
| C♯°7 | C♯ | E | G | B♭ |
| D°7 | D | F | A♭ | C♭ (B) |
| E♭°7 | E♭ | G♭ | B𝄫 (A) | D𝄫 (C) |
| E°7 | E | G | B♭ | D♭ |
| F°7 | F | A♭ | C♭ (B) | E𝄫 (D) |
| F♯°7 | F♯ | A | C | E♭ |
| G°7 | G | B♭ | D♭ | F♭ (E) |
| A♭°7 | A♭ | C♭ (B) | E𝄫 (D) | G𝄫 (F) |
| A°7 | A | C | E♭ | G♭ |
| B♭°7 | B♭ | D♭ | F♭ (E) | A𝄫 (G) |
| B°7 | B | D | F | A♭ |
The Big Idea
A diminished chord is built with 1 – ♭3 – ♭5. Its unstable sound makes it perfect for creating tension and leading into another chord. Add a ♭7 for a half-diminished chord, or stack one more minor 3rd to create a fully diminished 7th chord.