B Half-diminished 7th Chord

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Formula R – ♭3 – ♭5 – ♭7

Summary

B Half-diminished 7th is built from the notes B, D, F, A. The interval from B to D is a minor 3rd (3 semitones), from B to F is a tritone (6 semitones), from B to A is a minor 7th (10 semitones).

The half-diminished 7th, also written m7♭5 or ø7, is a dark, tense chord with a softer sound than a fully diminished chord. It often appears in minor-key harmony and is especially common in jazz and bossa nova.

Theory

Built from the root, minor third, diminished fifth, and minor seventh. It's called "half-diminished" because it looks similar to a fully diminished chord, but the top note is a minor 7th instead of a diminished 7th. In harmony, it often appears as the 2nd chord in minor keys, where it leads naturally into a dominant 7th and then resolves to the tonic.

On the guitar

Think of it as a minor 7th shape with a lowered 5th. On guitar, it works well as a compact 4-note voicing and connects very smoothly to dominant chords. The shape is comfortable on both 5th and 6th string roots.

Advanced

The half-diminished is one of the key sounds of minor-key resolutions (like Bm7♭5 → E7 → Am). More advanced players study it through drop 2, drop 3, and smooth voice-leading between chords. It has a reflective, unstable quality that makes it especially effective in ballads and harmonically rich progressions.

Piano