Diminished fifth

The diminished fifth (d5) spans 6 semitones and is one name for the tritone. It is a highly unstable interval that plays a central role in tension and resolution.

Construction and spelling

d5 is spelled as a fifth lowered by one semitone, such as C-Gb. Although it shares pitch distance with A4, its spelling indicates a contracted fifth function. This spelling choice matters for harmonic analysis.

Harmonic and melodic usage

Harmonically, d5 appears in dominant-function sonorities, diminished chords, and chromatic voice-leading. Melodically, it sounds dissonant and directional, often seeking resolution. In tonal harmony, the tritone is one of the main tension drivers.

Examples

• Tritone motion inside dominant seventh chords
• Diminished chord structures and altered harmony
• Chromatic lines emphasizing instability before cadence

In practice

Practice d5 from multiple roots and resolve it by contrary motion to stable intervals. Compare d5 with P5 to hear tension versus stability. Strong d5 recognition improves harmonic hearing and cadence awareness.