Cdim7
C Diminished 7th — perfectly symmetrical stacked minor thirds — the ultimate passing chord, able to resolve almost anywhere.
The keys
C – E♭ – G♭ – A
What's inside Cdim7
| Note | Interval from root | Degree |
|---|---|---|
| C | Root | 1 |
| E♭ | Minor 3rd | b3 |
| G♭ | Diminished 5th | b5 |
| A (spelled B♭♭) | Diminished 7th | bb7 |
Inversions
| Position | Keys (low → high) |
|---|---|
| Root position | C4 – E♭4 – G♭4 – A4 |
| 1st inversion | E♭4 – G♭4 – A4 – C5 |
| 2nd inversion | G♭4 – A4 – C5 – E♭5 |
| 3rd inversion | A4 – C5 – E♭5 – G♭5 |
A working voicing
Split the chord between two hands the way working players do — a solid shell low down, the colour tones up top:
| Hand | Keys |
|---|---|
| Left (shell) | C2 – A2 |
| Right (colour) | E♭4 – G♭4 |
Where Cdim7 lives
As the ii chord
Cdim7 → F7 → B♭maj7
Minor-family sevenths live on the ii — this is the move they were born for.
Stepwise colour
C → Cdim7 → Dm7
Used as a passing colour between neighbouring chords.
Put Cdim7 under your fingers
Hear every voicing, see the keys light up, and drill it in the interactive Chord & Voicing Lab.
Open the Chord & Voicing Lab →