Chord category
Diminished chords
The diminished chord stacks two minor thirds: dark, tense and unstable. It is written with dim or the ° symbol.
Theory
The diminished triad has the root, the minor third and the diminished fifth. Cdim7 adds one more minor third and is perfectly symmetric.
Formula and steps
Degrees
1 – ♭3 – ♭5
Steps (semitones)
3 – 3
How they are used
It works as a passing and tension chord: it connects two chords or substitutes a dominant. Its symmetry lets one shape serve four keys.
Progressions (roman numerals)
- I – ♯i° – ii
- vii° – I
Example sequences
- C – C♯° – Dm
- B° – C
Related chords
Alternative symbols
The triad is written Cdim or C°; with a seventh, Cdim7 or C°7. Do not confuse it with the half-diminished (Cm7♭5 or Cø), which has a minor seventh instead of the diminished one.