Half-diminished seventh chord
In music theory, the half-diminished seventh chord (also known as a half-diminished chord or a minor seventh flat five chord) is a seventh chord composed of a root note, together with a minor third, a diminished fifth, and a minor seventh (1, ♭3, ♭5, ♭7). For example, the half-diminished seventh chord built on B, commonly written as Bm7(♭5), or Bø7, has pitches B-D-F-A:
| Component intervals from root | |
|---|---|
| minor seventh | |
| diminished fifth (tritone) | |
| minor third | |
| root | |
| Tuning | |
| 5:6:7:9 or 25:30:36:45 | |
| Forte no. / | |
| 4-27 / |
It can be represented by the integer notation {0, 3, 6, 10}.
The half-diminished seventh chord exists in root position and in three inversions. The first inversion is enharmonic to a minor sixth chord:
In diatonic harmony, the half-diminished seventh chord occurs naturally on the seventh scale degree of any major scale (for example, Bø7 in C major) and is thus a leading-tone seventh chord in the major mode. Similarly, the chord also occurs on the second degree of any natural minor scale (e.g., Dø7 in C minor). It has been described as a "considerable instability".