Diminished seventh

The diminished seventh (d7) spans 9 semitones. It is a contracted seventh with dense chromatic function, especially in diminished harmony and enharmonic reinterpretation.

Construction and spelling

d7 is built by lowering a minor seventh by one semitone, for example C-Bbb. In equal temperament it can sound like M6, but the spelling indicates seventh-function context. This matters for harmonic grammar.

Harmonic and melodic usage

Harmonically, d7 appears inside fully diminished seventh chords and dramatic chromatic progressions. Melodically, it carries tense color and directional intent. Its notation often clarifies resolution pathways.

Examples

• Fully diminished seventh chord spellings
• Enharmonic pivots in modulation passages
• Chromatic dominant-preparation gestures

In practice

Practice reading and singing d7 spellings with double accidentals. Compare d7 with M6 to separate interval function from equal-tempered sound. This builds stronger analysis and voice-leading awareness.