Half-diminished seventh chord
| Component intervals from root | |
|---|---|
| flat seventh | |
| diminished fifth (tritone) | |
| minor third | |
| root | |
| Tuning | |
| 5:6:7:9 or 25:30:36:45 | |
|
Forte no. / |
|
| 4-27 / |
In music theory, the half-diminished seventh chord—also known as a half-diminished chord or a minor seventh flat five (m7♭5)—is formed by a root note, a minor third, a diminished fifth, and a flat seventh. Its consecutive intervals are minor third, minor third, major third.
It can be created by playing the tonic, flattened third, flattened fifth, and flattened seventh degrees of any major scale (1, ♭3, ♭5 and ♭7)—for example, C half-diminished is (C E♭ G♭ B♭). Alternatively, it can be derived simply by raising (by a semitone) the root note of the major seventh chord.
In diatonic harmony, the half-diminished chord occurs naturally on the seventh scale degree of any major scale (for example, Bø7 in C major). By the same virtue, it also occurs on the second degree of any natural minor scale (e.g., Dø7 in C minor). It occurs as a leading-tone seventh chord in major and can be represented by the integer notation {0, 3, 6, 10}. It has been described as a "considerable instability".
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