A diminished chord is composed using a root/1st, minor 3rd and a diminished 5th (or R/1-♭3-♭5) intervals played simultaneously. Generally written as C⁰, C⁰ or Cmi(♭5), it is good practice to simply use an upper case C and a super scripted lowercase ⁰ (ie: C⁰) to represent it in writing.
The tonality of a diminished chord is dissonant, non-centered and unstable (as opposed to a major chord which is stable and resolved), and is in need of resolution to the root. The diminished chord occurs naturally in the harmonized major scale at the seventh degree, for example: in the key of C major, B⁰ is the VII chord.
Diminished chord profile
|Intervals||root/1st, minor 3rd, diminished 5th or R/1-♭3-♭5|
|Stability||Dissonant, unstable, unresolved|
|Common names (examples in C)||C⁰, Cdim, Cmi(♭5)|
Diminished chord table
|Chord name||Root||Minor third||Diminished fifth|
|D♭⁰||D♭||F♭ (E)||A (G)|
|G♭⁰||G♭||B (A)||D (C)|
|A♭⁰||A♭||C♭ (B)||E (D)|
|D diminished chord voicing #1|