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Chord type

Diminished Chords on Piano

The diminished chord is a dissonant triad built from two minor thirds, creating a dark, tense, and unstable sound that demands resolution. It is used as a passing chord, a dramatic tension builder, and a key-change pivot in classical, jazz, and film music.

Pick a key to hear and see it below. Each key opens a full reference entry with a keyboard diagram, audio, inversions, fingerings, and notation.

Featured key

C Diminished Chord

Notes: C - E♭ - G♭

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Open the full C Diminished Chord reference ›
Formula: Root – Minor 3rd – Diminished 5th
Intervals: 3 + 3 semitones (two stacked minor thirds)
Scale degrees: 1–♭3–♭5
Sound: Tense, dark, unstable, dramatic
Symbol: dim or ° (Cdim, C° etc.)
Diminished vs Half-Diminished vs Diminished 7th: The diminished triad (1–♭3–♭5) is the foundation. Add a minor 7th and you get half-diminished (m7♭5). Add a diminished 7th and you get fully diminished 7th (dim7). Each has a different level of tension and function in harmony.

Diminished vs diminished 7th vs m7♭5

All three are built on the same diminished triad (C, E♭, G♭). What sits on top is the whole difference.

ChordFormulaNotes on CCharacter
C°1 ♭3 ♭5C, E♭, G♭Two stacked minor thirds. Tense and unstable, it wants to resolve.
C°71 ♭3 ♭5 ♭♭7C, E♭, G♭, B♭♭Three stacked minor thirds. Symmetrical and maximally restless; any note can act as the root.
Cm7♭51 ♭3 ♭5 ♭7C, E♭, G♭, B♭A diminished triad plus a minor seventh. Darker than minor; it is the ii chord of every minor key.

C°7’s top note, B♭♭ (B double-flat), is enharmonically A. The three cross-links open the full reference for each chord type.

C1C2C3CB♭♭C5C6C7C8E♭G♭

C°7: C, E♭, G♭, B♭♭. Three stacked minor thirds. Symmetrical and maximally restless; any note can act as the root.

Common questions

What is the difference between a diminished and a diminished 7th chord?

A diminished chord (C°) is a three-note triad: C, E♭, G♭. A diminished 7th chord (C°7) adds a fourth note another minor third up, B double-flat (enharmonically A): C, E♭, G♭, B♭♭. The triad is tense; the 7th chord is fully symmetrical and even more restless.

Is m7♭5 the same as a diminished chord?

No. A minor 7th flat five (Cm7♭5), also called half-diminished, is a diminished triad plus a minor seventh: C, E♭, G♭, B♭. Its seventh is a minor seventh (B♭), whereas a diminished 7th chord uses a diminished seventh (B♭♭). The half-diminished sounds softer and is the ii chord in minor keys.

Why is m7♭5 called half-diminished?

Because only the fifth is diminished, not the seventh. A fully diminished 7th chord lowers both the fifth and the seventh; the half-diminished lowers just the fifth and keeps an ordinary minor seventh.

Diminished Chord in All 18 Keys

All 18 spellings, ♯ and ♭ keys listed separately.

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C Diminished ChordNotes: C – E♭ – G♭C♯ Diminished ChordNotes: C♯ – E – GD♭ Diminished ChordNotes: D♭ – F♭ – A♭♭D Diminished ChordNotes: D – F – A♭D♯ Diminished ChordNotes: D♯ – F♯ – AE♭ Diminished ChordNotes: E♭ – G♭ – B♭♭E Diminished ChordNotes: E – G – B♭F Diminished ChordNotes: F – A♭ – C♭F♯ Diminished ChordNotes: F♯ – A – CG♭ Diminished ChordNotes: G♭ – B♭♭ – D♭♭G Diminished ChordNotes: G – B♭ – D♭G♯ Diminished ChordNotes: G♯ – B – DA♭ Diminished ChordNotes: A♭ – C♭ – E♭♭A Diminished ChordNotes: A – C – E♭A♯ Diminished ChordNotes: A♯ – C♯ – EB♭ Diminished ChordNotes: B♭ – D♭ – F♭B Diminished ChordNotes: B – D – FC♭ Diminished ChordNotes: C♭ – E♭♭ – G♭♭