Half-diminished seventh chord
The half-diminished seventh chord is a four-note chord made of a diminished triad and a minor seventh, written m7♭5 or with the sign ø. It is typical of minor cadences. A single note distinguishes it from the diminished seventh chord, the seventh.
- Structure
- diminished triad + minor seventh
- Thirds
- minor – minor – major (3 + 3 + 4 semitones)
- Notation
- m7♭5 (for example Bm7♭5), also ø
- Example
- B–D–F–A
- Degree in A minor
- ii, with seventh ii ø7
- Not to be confused with
- diminished seventh chord (3 + 3 + 3)
One note's difference from the diminished seventh chord
The page Chords lists the most important seventh chords. If you stack a further third on a triad, a seventh chord with four notes arises. The half-diminished consists of a diminished triad plus a minor seventh and, according to the page, is typical in minor cadences.
| Seventh chord | Structure | Example | Effect according to the Chords page |
|---|---|---|---|
| Dominant seventh chord | major triad + minor seventh | G7 | full of tension, presses to the tonic |
| Major seventh chord (maj7) | major triad + major seventh | Cmaj7 | soft, jazzy, floating |
| Minor seventh chord (m7) | minor triad + minor seventh | Dm7 | round and mild |
| Half-diminished seventh chord (m7♭5) | diminished triad + minor seventh | Bm7♭5 | typical in minor cadences |
The name “half-diminished” expresses how far the chord is from the diminished seventh chord. Its three minor thirds give, according to the article The diminished seventh, four notes at an equal distance: from C: C, E♭, G♭, B♭♭ (sounds like A). In the half-diminished chord the top note is a semitone higher. The minor third on top is replaced by a major one.
Half-diminished: B–D–F–A
Two minor thirds form the diminished triad B–D–F. The minor seventh A is added on top, a major third above F. The diminished fifth B–F is contained in the chord.
Diminished: B–D–F–A♭
The diminished seventh chord has three minor thirds. Instead of A there is A♭, the seventh is a semitone smaller. Only this one note distinguishes the two chords.
The diminished fifth in the chord
The triad inside consists of two minor thirds. Its fifth is, as the page Chords describes, reduced instead of perfect, and that is why it sounds tense and restless. In the half-diminished chord a diminished fifth therefore lies between root and fifth, in the example B–F. The page Diatonic chords explains the sign ° at vii: a diminished triad, tense and restless, which mostly presses to the tonic.
In the minor cadence
In minor the diminished triad is built on the second degree, in A minor that is B°. With the minor seventh A above it, this becomes the half-diminished seventh chord. In the cadence it leads to the dominant and to the tonic. Hear the path Bm7♭5 – E7 – Am:
The dominant E7 carries the leading tone G♯ from harmonic minor. See also Cadences.
Common mistakes
- Confusing half-diminished and diminished: The diminished seventh chord has three minor thirds, the half-diminished minor, minor, major. Only the top note is different.
- Forgetting the seventh: Without the minor seventh a diminished triad is left.
- Reading the sign wrongly: m7♭5 means minor seventh chord with a diminished fifth, not “minor plus flat”.
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Related terms
Diminished seventh chordDiminished triadSeventh chordDominant seventh chordDiminished fifthDiatonic chordCadenceTritone
Editor: Maik Krohm · reviewed on 3 October 2026
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