semicord

Cdim C diminished chord

Notes
C Eb Gb
Formula
1 b3 b5
Semitones
0 3 6 above the root
Other symbols
C°, Cm(b5)

C to Eb is a minor third (3 semitones), Eb to Gb is a minor third (3 semitones). Two minor thirds stacked, so C to Gb is a tritone (6 semitones) instead of a perfect fifth. The four-note Cdim7 and Cm7b5 grow from it by adding a note on top.

Cdim on the piano

C4D4E4F4G4A4B4C5D5E5F5G5A5B5C#4Eb4Gb4Ab4Bb4C#5Eb5F#5Ab5Bb5CC4EbGbC5

Root position from C4: C4, Eb4, Gb4. Middle C is C4.

Cdim on the guitar

Standard tuning (E A D G B E). Strings run low E on the left to high e on the right, frets downwards; × is a muted string, ○ an open string, and each dot shows the note it sounds, with the root in blue-green. Every shape below has C as its lowest note.

×CCGbGbCCEbEb×
A-shape barre, root on the A string at fret 3
x 3 4 5 4 x (low E to high e)
Sounds C3 Gb3 C4 Eb4
8frCCGbGbCCEbEb××
E-shape barre, root on the E string at fret 8
8 9 10 8 x x (low E to high e)
Sounds C3 Gb3 C4 Eb4

The barre shapes are movable: an E-shape chord's root is the note under your first finger on the low E string, an A-shape chord's root is the note on the A string. Slide the same grip up or down to play diminished chords on other roots.

Inversions of Cdim

An inversion puts a note other than the root in the bass. The name is what semicord's chord finder calls those notes played bottom to top; a slash name like C/E means a C chord with E in the bass.

PositionNotes, bass firstNamedListen
Root positionC Eb GbCdim
1st inversionEb Gb CCdim/Eb
2nd inversionGb C EbCdim/Gb

Where Cdim fits

Cdim is vii° in Db major, ii° in Bb minor, vii° in C# minor (where it is spelled B#dim). Its root C is the leading tone of Db: a half step below the tonic, so the chord usually moves up to it.