The Diminished Chord
A diminished chord is built from two stacked minor thirds, which puts a tense tritone between its root and its flattened fifth.
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How is a diminished chord built, and what makes it sound so tense?
Picture a movie moment where the music suddenly feels unsettled—that’s often a diminished chord. What interval creates that eerie tension?
Many listeners expect a chord with a minor third to sound comfortably minor. Diminished chords have a minor third, but they sound unstable—why?
Compare semitone stacks: major is 4+3, minor is 3+4, diminished is 3+3. Highlight the 6-semitone tritone between root and fifth.
If you can lower the fifth of any minor triad by one semitone, you can build and recognize a diminished chord—and understand why it feels tense.
- diminished seventh chords
- inversions
- voice leading
- harmonic function
- 01The Suspense ChordslideSlot 1Hook
Think of the chord that makes a movie feel unsettled. It usually isn't major or minor—it's diminished. Let's find the interval pattern behind that unease.
- A diminished chord sounds tense and unstable
- It is not a major or minor triad
- Its identity comes from the exact intervals stacked above the root
PhenomenonA single chord can instantly change the mood from bright to suspenseful.
QuestionWhat interval pattern creates that unsettled feeling?
- 02Major vs Minor vs DiminishedslideSlot 2Tension
You know major and minor triads. A diminished triad seems close to minor, but it doesn't behave like one. What changed?
- Major: root, major third, perfect fifth
- Minor: root, minor third, perfect fifth
- Diminished: root, minor third, diminished fifth
PredictionIf a chord has a minor third, it should feel like a minor chord.
Tempting intuitionBecause diminished has a minor third, many people expect it to sit comfortably like a minor chord—but the lowered fifth destroys that stability.
- 03Build the Diminished TriadinteractiveSlot 3Reveal
Start with C major, then make the changes step by step: lower the third, then lower the fifth. Watch the semitone gaps become two equal minor thirds.
- C major = C-E-G: 4 semitones + 3 semitones
- C minor = C-Eb-G: 3 semitones + 4 semitones
- C diminished = C-Eb-Gb: 3 semitones + 3 semitones, with a tritone between C and Gb
EvidenceCompare semitone counts: major 4+3, minor 3+4, diminished 3+3. The root and fifth of a diminished triad are 6 semitones apart—a tritone.
ConclusionA diminished chord isn't just a slightly altered minor chord; its two equal minor-third layers produce a tense, unresolved sound.
Mechanism- 1Start with a minor triad: root, minor third, perfect fifth.
- 2Lower the fifth by one semitone, turning the perfect fifth into a diminished fifth.
- 3Now the fifth is a tritone above the root, and the chord is made of two stacked minor thirds that pull against each other.
- 04Spotting Diminished ChordsslideSlot 4Takeaway
Use the same rule anywhere: lower the fifth of a minor triad by one semitone and you have a diminished triad.
- Find the root
- Add a minor third above it
- Add another minor third above that (or lower the fifth of a minor triad)
TransferTry identifying Ddim: start from D-F-A, lower the A to Ab, and you get D-F-Ab—the same two-minor-thirds stack.
Expected inferenceAny diminished triad will have the same tense tritone between root and fifth, so you can recognize one by counting three-semitone steps from the root.
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