Common-tone diminished seventh chord
| Component intervals from root | |
|---|---|
| diminished seventh | |
| diminished fifth (tritone) | |
| minor third | |
| root | |
| Tuning | |
| 125:150:180:216 | |
|
Forte no. / |
|
| 4–28 / |
The diminished seventh chord is commonly used in the harmony of both Western classical music and also in jazz and popular music of the twentieth and twenty-first centuries. Classical composers of the eighteenth and nineteenth centuries imaginatively exploited the chord's dramatic and expressive potential. (See below).
A diminished seventh chord is a four note chord that comprises a diminished triad plus the interval of a diminished seventh (alternatively regarded enharmonically as a major sixth) above the root. Thus it is (1, ♭3, ♭5, 
7), or enharmonically (1, ♭3, ♭5, ♮6), of any minor scale; for example, C diminished-seventh would be (C, E♭, G♭, B), or enharmonically (C, E♭, G♭, A). It occurs as a leading-tone seventh chord in harmonic minor and can be represented by the integer notation {0, 3, 6, 9}.
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