Chord Shapes

Diminished 7th

Intervals: 1-b3-b5-bb7 (enharmonically a major 6th). A stack of minor 3rds dividing the octave into four equal parts. This symmetry means any note can be treated as the root and the same shape can resolve to several different targets. The dim7 chord is one of the most dissonant sonorities in common-practice harmony and in jazz is usually used briefly as a passing, approach or substitute dominant chord. A fully diminished chord a semitone above a target minor or major chord will resolve smoothly by step (e.g. C#°7 → Dm7 in “Misty”). Dim7 chords also stand in for V7b9 built on the dominant’s 3rd (e.g. B°7 implying G7b9). Use them for chromatic approach lines, rootless V7b9 substitutions and dramatic “crisis” moments before a resolution.