The diminished triad stacks two minor thirds, producing 1-♭3-♭5. Between root and fifth you hear a diminished fifth (tritone), which makes the chord inherently unstable and strongly directional. It appears diatonically in major keys on vii° and in minor keys on ii°, and it is a basic building block for diminished scales and passing harmony in classical, jazz, and pop.
Construction
Formula: 1-♭3-♭5. In Cdim, spell C-E♭-G♭.
Usage
Use as leading-tone harmony, chromatic passing chords between diatonic triads, and as the upper part of larger dominant-type voicings (especially with a bass note a third below the chord root).
Examples
- Baroque and classical sequences with vii° as dominant substitute
- Jazz “common-tone diminished” passages
- Pop pre-chorus lifts with chromatic bass motion
Play
Voice compactly for clarity, avoid doubling the leading tone clumsily in classical voice leading, and resolve the tritone by contrary motion when possible.
Ear-training cues
Two minor thirds in a row; a tight, restless, “crunched” minor color with a tritone shell.
