What Is a Diminished Triad?
A diminished triad is a three-note chord that sounds tense, unstable, and incomplete. It's built from a root note, a minor third, and a diminished fifth — a flattened perfect fifth.
Diminished triads are unique: they don't sound like home. Instead, they sound like they need to go somewhere. This tension is intentional — it's what makes them useful in music. Diminished triads create forward momentum. They want to resolve.
How to Build a Diminished Triad
Formula
Root + 3 semitones + 3 semitones
Or: Root + Minor 3rd + Diminished 5th
To build any diminished triad, pick a root note and count up from there.
Example: C Diminished Triad
- C (root)
- E♭ (3 semitones up from C = minor third)
- G♭ (3 semitones up from E♭ = diminished fifth, or 6 semitones up from C)
The diminished fifth — exactly 6 semitones — is what creates the tension. In a perfect fifth (7 semitones), the chord feels complete. Flatten it by a semitone and suddenly the chord sounds wrong, incomplete, demanding resolution.
All 12 Diminished Triads
| Chord | Root | Minor 3rd | Diminished 5th |
|---|---|---|---|
| C° | C | E♭ | G♭ |
| G° | G | B♭ | D♭ |
| D° | D | F | A♭ |
| A° | A | C | E♭ |
| E° | E | G | B♭ |
| B° | B | D | F |
| F#° | F# | A | C |
| F° | F | A♭ | B |
| B♭° | B♭ | D♭ | F♭ |
| E♭° | E♭ | G♭ | A |
| A♭° | A♭ | C♭ | E♭♭ |
| D♭° | D♭ | F♭ | A♭♭ |
The Sound of a Diminished Triad
Tense, unstable, incomplete, wanting resolution, eerie, unsettling.
Diminished triads sound wrong on purpose. They're useful not as destination chords but as passing chords — chords that create tension and then resolve to a major or minor triad. A diminished chord followed by a resolved major chord creates a powerful sense of arrival.
Diminished Triads in Keys
In any major scale, there's exactly one diminished triad: the vii° chord built on the 7th scale degree.
C Major scale: The vii° chord is B diminished (B D F)
Key characteristic: The vii° naturally wants to resolve up to the I chord (B diminished → C Major)
This resolution is so natural that diminished chords are often used leading into the home chord. The tritone interval in the diminished chord creates harmonic tension that demands release.
How to Use Diminished Triads
1. As a leading tone chord: Use the vii° right before the I chord to create arrival and resolution.
2. In jazz: Diminished 7th chords (diminished triads with an added 7th) are everywhere in jazz harmony as passing chords and chromatic bridges.
3. For dramatic effect: Use diminished chords in minor-key compositions to intensify emotion or create danger.
4. In voice leading: Diminished triads can help smooth transitions between chords by providing chromatic movement.
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Learn to identify the tense quality of diminished triads instantly by ear.