Diminished chord: what it is and how to build it
A diminished chord is a triad made of two stacked minor thirds: root, minor third and diminished fifth, 3 + 3 half steps. It sounds tense and unstable. Adding a diminished seventh makes a four-note diminished seventh chord.
A diminished chord is a three-note chord that sounds tense, as if it is leaning forward and asking to move on. It is built by stacking two minor thirds. That makes it the smallest and tightest of the four basic triad types. You will hear it in classical music, jazz and in the dramatic moments of film scores.
This page shows you how to build one on any note, where it fits in a key, what its symbols look like and how it differs from its close relatives, the diminished seventh and the half-diminished chord.
How do you build a diminished chord?
Start with any note as the root. Count 3 half steps up to reach the third. Count 3 more to reach the fifth. That is the whole formula: 3 + 3. Compare it with a minor chord, which is 3 + 4, and a major chord, which is 4 + 3.
Another way to say it: take a minor chord and lower the fifth by one half step. The interval from the root to the fifth is then six half steps, which is a diminished fifth, also called a tritone. That interval is what gives the chord its restless sound.
| Step | Interval from the root | Half steps from the root |
|---|---|---|
| Root | unison | 0 |
| Third | minor third | 3 |
| Fifth | diminished fifth | 6 |
How do you write a diminished chord symbol?
The usual symbols are the root plus dim (Cdim), a small circle (C°) or the word diminished. In Roman numeral analysis a small circle follows a lowercase numeral, as in vii°. Some people write the chord as Cm♭5, which also names a minor chord with a lowered fifth. All of these mean the same triad.
Take care not to mix up the symbol ° with the symbol ø. A circle with a slash through it, as in Cø7, means a half-diminished seventh chord, which is a different four-note chord. The page on the half-diminished chord explains the difference.
Where does a diminished chord appear in a key?
In a major key, the triad on the seventh note is diminished. In C major that is B, D and F, written B°. The chord is made of notes only from the C major scale, so it belongs to the key. In a natural minor key, the triad on the second note is diminished. In A minor that is B, D, F again.
The vii° chord often takes the place of a V7 chord, because it shares the same tension notes. It sounds like a dominant seventh with the root left out. That is why it usually leads strongly to the tonic. For more on keys and chords see chord progressions.
What is a diminished seventh chord?
Add a fourth note a minor third above the diminished fifth and you get a diminished seventh chord. Its formula is 3 + 3 + 3. The symbol is dim7 or °7. The seventh here is 9 half steps above the root, which is called a diminished seventh, and it sounds the same as a major sixth.
The diminished seventh chord is perfectly symmetrical. Every note is three half steps from the next, and the last note is three half steps below the root's octave. That means the same four sounds can be named as a chord built on E♭, G♭ or A as well as C. Because it has no clear home note, composers use it to modulate, or change key, quickly.
How does a diminished chord sound?
Diminished chords sound tense, mysterious or suspenseful. Because the fifth is smaller than usual, the chord does not feel stable or at rest. In older classical music it often marked drama or surprise. In jazz it is used as a passing chord that links two other chords by step. In horror and thriller soundtracks you will often hear sustained diminished chords.
What are the twelve diminished triads?
Every note can be a root, so there are twelve diminished triads. You can open any of them on the site, starting with C diminished and F♯ diminished. Each page shows the notes, a piano diagram and a staff.
How can you practice diminished chords?
- Play a C minor chord (C, E♭, G).
- Lower the G to G♭ and listen to how the chord tightens.
- Move the whole shape up one half step at a time and check each chord by counting 3 + 3.
- Play the vii° chord of C major, B diminished, and resolve it to C major.
Memory trick: diminished means smaller. A minor chord has a perfect fifth, and diminishing it makes the fifth smaller by one half step, from 7 to 6.
Check yourself
1. What is the half step formula for a diminished triad?
Answer: 3 + 3. Two minor thirds stacked make a diminished triad.
2. Which interval is between the root and fifth of a diminished triad?
Answer: Diminished fifth. The fifth is lowered to 6 half steps, which is a diminished fifth or tritone.
3. Where is the diminished triad in a major key?
Answer: On the seventh note. The vii° chord is the only diminished triad in a major key.
4. How many half steps does a diminished seventh chord stack between each note?
Answer: 3. Diminished seventh chords are 3 + 3 + 3, so every interval is 3 half steps.
5. Which symbol means a half-diminished seventh chord?
Answer: Cø7. A circle with a slash is half-diminished, while a plain circle is fully diminished.