Root–minor third–diminished fifth; tense, unstable; often functions as leading-tone.
Diminished Triad
The Diminished Triad is the most tense and unstable of the basic triads.
It appears naturally in both major and minor keys but rarely stands alone for long — instead, it functions as a passing or leading chord, creating dramatic pull toward resolution.
Its instability comes from its flattened fifth, which narrows the normally perfect interval between root and fifth and introduces a biting dissonance.
Structure
A diminished triad is formed by stacking two minor thirds on top of each other.
Formula:
Root – Minor 3rd – Diminished 5th
Semitone steps from root: 0 – 3 – 6
Example (B Diminished Triad):
B – D – F
| Interval | Distance | Note | Function |
|---|---|---|---|
| Root | 0 | B | Tonal center (unstable) |
| Minor 3rd | +3 | D | Dark, tense interval |
| Diminished 5th | +6 | F | Disrupts consonance; creates pull upward |
Interval Structure (Stacked Thirds)
| From | To | Interval | Size | Result |
|---|---|---|---|---|
| Root → 3rd | Minor 3rd | 3 semitones | Minor color | |
| 3rd → 5th | Minor 3rd | 3 semitones | Adds symmetry, tension | |
| Root → 5th | Diminished 5th | 6 semitones | Unstable “tritone” interval |
The diminished fifth (or tritone) divides the octave exactly in half — it resists resolution until it moves to a more stable interval.
Inversions
| Inversion | Notes (B Dim) | Symbol | Bass Note | Function |
|---|---|---|---|---|
| Root Position | B–D–F | Bdim | B | Sharp tension, leading tone chord |
| 1st Inversion | D–F–B | Bdim/D | D | Softer but still unstable |
| 2nd Inversion | F–B–D | Bdim/F | F | Often used as a pivot or passing chord |
Roman Numeral Function
| Scale Degree | In Major Key | In Minor Key | Function |
|---|---|---|---|
| vii° | Diminished | – | Leading-tone chord to tonic |
| ii° | – | Diminished | Subdominant area (pre-dominant) |
In major keys, the diminished triad occurs naturally on the 7th degree (vii°).
It typically resolves to the tonic (I) because its root and fifth both move by semitone — the essence of tonal gravity.
Emotional Character
- Mood: tense, unstable, suspenseful.
- Stability: lowest of all triads — wants to resolve immediately.
- Role: transitional — creates movement between chords or modulates to a new key.
- Texture: feels “compressed,” lacking the openness of major/minor triads.
The diminished triad’s dissonance gives it expressive power — composers use it to heighten tension or signal impending resolution.
Real-World Examples
| Song | Artist | Key | Usage |
|---|---|---|---|
| “Because” | The Beatles | A Minor | Bdim between Am and C creates chromatic lift |
| “Michelle” | The Beatles | F Major | Ddim leads gracefully to Dm |
| “Every Breath You Take” | The Police | A Major | F♯dim passing between A and E chords |
| “My Funny Valentine” | Rodgers & Hart | C Minor | Diminished chords as elegant passing tones |
| “Yesterday” | The Beatles | F Major | Edim resolves smoothly to Fmaj |
Application Tips
- Voice leading: resolve the root up a semitone, and the fifth down a semitone for smooth motion.
- Guitar: diminished triads repeat every 3 frets — symmetrical shape.
- Piano: use diminished triads for connecting motion (e.g., I → I#° → ii).
- Composition: ideal between two chords a tone apart — creates chromatic bass movement.
Summary
| Attribute | Value |
|---|---|
| Formula | 1 – ♭3 – ♭5 |
| Semitones | 0 – 3 – 6 |
| Tonality | Dissonant / unstable |
| Emotional Color | Tense, suspenseful, transitional |
| Function | Leading-tone or passing chord |
| Inversions | Root, 1st, 2nd |
| Common Progressions | vii°–I, ii°–V, I–I#°–ii |
| Used In | Classical, jazz, Beatles-style chromatic writing, film music |