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The Cdim chord

Built from C - D# - F#, the Cdim is a diminished triad that sounds unstable, tense, transitional. It lives at the centre of jazz turnarounds and ragtime piano, and it shows up in more songs than you would expect. A passing chord between two stable major chords. Ragtime piano lives on it. What follows below: the voicings worth memorising on guitar and piano, the theory in plain language, progressions in two or three different keys, and a short list of real records that lean on the chord.

Hear the Cdim in the chord builder →

Voicings for Cdim

Common ways to grip the Cdim on guitar and piano. Guitar diagrams read low E to high E left-to-right; an × means muted, an open circle above the nut means an open string. Filled dots are fretted notes.

Guitar , full chord shapes

CAGED-derived voicings for Cdim across the neck. Pick the shape closest to where your hand already sits.

Guitar: A-string dim at fr.3

Notes: C - D# - F# (chord tones)

Guitar: D-string dim at fr.10

Notes: C - D# - F# (chord tones)

Guitar: top-4 voicing

Notes: C - D# - F# (chord tones)

Guitar: high top-4 voicing

Notes: C - D# - F# (chord tones)

Guitar , triad shapes

Three-note voicings on three adjacent strings. Light textures for arpeggios, pop layering and chord-melody work.

Triad: top-string triad

Notes: 3-note voicing on adjacent strings

Triad: middle-string triad

Notes: 3-note voicing on adjacent strings

Triad: bass-side triad

Notes: 3-note voicing on adjacent strings

Piano voicings

Root position and inversions. The bass note matters: each inversion changes how the chord sits under a melody.

Piano: root position

Notes: C - D# - F#. Root C at the bottom. The classic stacked-thirds spelling of a diminished triad.

Piano: first inversion

Notes: D# - F# - C. D# at the bottom. Common in chord-melody, walking bass lines and gentler voicings.

Piano: second inversion

Notes: F# - C - D#. F# at the bottom. A floating, suspended feel often used in hymns and ballads.

The theory behind Cdim

The Cdim chord (C - D# - F#) is a diminished triad. Its intervals are root, minor third, diminished fifth. Functionally it lives at home in Db major as the Leading tone (vii°), but you'll also find it in Bb minor as the Supertonic (ii°). The chord tends to resolve up a half-step or down to the I, which is why it shows up in ragtime and jazz.

Progressions that use Cdim

Short progressions that put the Cdim to work. Each one is shown in a different key so you can pick the one that suits your singer.

i→iv→V key of A minor

Cdim (as passing colour)

This chord appears as a borrowed or passing chord in many minor-key progressions.

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Songs that feature Cdim

Real records where this chord does structural work. No lyrics quoted, just the title and artist so you can pull up a copy and hear it in context.

My Funny Valentine by Standard. Cdim as a passing chord between two diatonic chords.
Sweet Georgia Brown by Standard. Cdim within the ragtime turnaround.
Take the A Train by Duke Ellington. Cdim colour in the verse.

Related chords

Chords a step away from the Cdim in the songwriting circle, the natural neighbours when you want a substitution.

TriadC DomC7 Maj7Cmaj7 m7Cm7 NeighbourG NeighbourGm NeighbourG7 NeighbourF

Keys where Cdim lives

The keys where this chord turns up diatonically. Open any key page for the full set of progressions that lean on it.

Db major Bb minor

More songwriting tools

Got the chord but still wrestling with the lyric? Find the right rhyme in RhymeForge, or break a writer's block with the unexpected word-pair generator in CollisionLab. Need to map a full progression? The chord builder on the home page is where the Cdim fits into context. All free, no signup.

About the chord builder

The Undercover Zest chord progression builder is a free interactive tool that maps every diatonic and borrowed chord in every key. Click a Roman numeral to hear it, drag chords into a progression, then audition voicings, inversions and tensions until the song clicks.

This page is a static reference for the Cdim. For interactive playback, voice-leading hints and substitution suggestions, open the chord builder above.