Half-Diminished Seventh Chord
A minor seventh chord with the fifth pushed down one key: C, E flat, G flat and B flat. The name sounds like an exam question, but the chord has one main job, and once you know where it sits you hear it everywhere in minor key jazz.
- 4 notes
- 1 b3 b5 b7
- leaning
which styles use it
- Jazz
- Bossa nova
- Film music
- Neo-soul
Which notes are in a half-diminished seventh?
A diminished triad with a minor seventh on top. In C: C, E flat, G flat and B flat.
- C, the root
- E flat, the minor third
- G flat, the diminished fifth
- B flat, the minor seventh
Why is it only half diminished?
Because only the bottom half of the chord is. Stack three minor thirds and you get a fully diminished seventh, where every gap is the same size. Here the top interval is a major third instead, so the symmetry breaks and the chord keeps a clear root.
That one difference is what you hear. The tritone between the root and the fifth makes it wobble from the inside, but it wobbles in a direction, where a dim7 simply hangs. Melancholy rather than alarming.
Where do you find it?
Two places, and both are worth knowing.
In a minor key it sits on the second degree, which makes it the front half of the minor ii V i: Dm7b5, G7, Cm. That is the move this chord exists for, and it runs through jazz and bossa nova.
In a major key it sits on the seventh degree. In C that is Bm7b5, doing the same job the diminished triad does: leaning towards home.
Cm7b5, Cm7 or Cdim7?
Three chords with a minor third at the bottom, one note apart each time.
- Cm7 (C Eb G Bb) - Perfect fifth, so the chord stands still and can loop all day.
- Cm7b5 (C Eb Gb Bb) - Drop that fifth and it starts leaning. Still has a root, still points somewhere.
- Cdim7 (C Eb Gb Bbb) - Drop the seventh as well and every gap is a minor third. Now nothing is the root and it can go almost anywhere.
Common mistakes
- Reading the name as a warning
Half diminished sounds worse than it is. It is a m7 with one note moved, and it resolves in the most ordinary way there is.
- Forgetting that the bass decides
C, E flat, G flat and B flat are also the notes of E flat minor 6. Which chord a listener hears depends on the bottom note and on where the music is heading.
Keep going
Everything in chords
- Half-Diminished Seventh Chord
- What Is a Chord?