C Diminished Chord (Cdim)

1Composition: what it contains

C – E♭ – G♭

Symbol

Cdim

Also written

Cdim, C°, Cm♭5, Cmi(♭5)

Formula

1 ♭3 ♭5

2Appearance: diagrams and sound

On the guitar

On the ukulele

On the piano

On the staff

On bass and as an arpeggio

3Indications: what it is used for

The vii° chord of a major key and the ii° chord of a minor key are diminished triads. It works as a leading-tone chord resolving to the tonic (vii°–I), as a passing chord between two diatonic chords (for example between I and ii, or IV and V), and as an incomplete dominant seventh: the vii° triad contains the 3, 5 and 7 of V7. Classical, jazz, gospel and film music use it for tension and chromatic movement in the bass.

4Dosage: how to practise it

On piano, play the triad in all inversions at 60 BPM, then practise vii°6–I resolutions with smooth voice leading (the diminished fifth contracting to a third). On guitar, learn the compact three-string shapes on the top strings and the shape rooted on the fifth string. Practise the passing progression I–♯I°–ii–V slowly, then at 80–100 BPM. Arpeggiate 1-♭3-♭5 on bass. Five minutes a day is enough once the shapes are known.

5Warnings and common mistakes

Do not confuse the triad (dim) with the diminished seventh chord (dim7 or °7) or the half-diminished seventh (m7♭5 or ø7): many charts write 'dim' when they mean the four-note dim7, so check the style. The diminished fifth is not a perfect fifth; on guitar, power-chord habits make players play the wrong fifth. In root position the triad can sound harsh; first inversion is the most common classical voicing.

6Interactions with chords, scales and keys

Inversions

• Inversion 1 · Cdim/E♭ · E♭ – G♭ – C Play
• Inversion 2 · Cdim/G♭ · G♭ – C – E♭ Play

Scales to play over Cdim

• C Locrian Mode
• C Blues Scale
• C Half-Whole Diminished Scale
• C Whole-Half Diminished Scale
• C Hungarian Minor Scale
• C Altered Scale

Where it appears (keys and Roman numerals)

• vii° – Key of C sharp Major
• vii° – Key of D flat Major
• ii° – Key of A sharp Minor
• ii° – Key of B flat Minor

7Other presentations available

The same chord from every note

C♯dim Ddim E♭dim Edim Fdim F♯dim Gdim A♭dim Adim B♭dim Bdim

Other chords on C

C Cm Caug Csus2 Csus4 C5 C6 Cm6 C7 Cmaj7 Cm7 Cm7♭5 Cdim7 Cm(maj7) C7sus4 Cadd9 Cm(add9) C6/9 C9 Cmaj9 Cm9 C11 Cm11 C13 C7♭9 C7♯9 C7♯5 C7♭5