Sevenths
B♭ half-diminished 7th chord
Dark and unresolved; often the ii chord in a minor key.
B♭m7♭5 is the viiø7 chord in B major. In minor keys: iiø7 in G♯ minor.
- Notes
- B♭D♭F♭A♭
- Formula
- 1♭3♭5♭7
- Built from
- root · minor 3rd · diminished 5th · minor 7th
How to play B♭m7♭5
About the B♭ half-diminished 7th chord
Playing it
On guitar, B♭m7♭5 has an open-position shape, x12120, using four fingers alongside the open strings. Don’t strum the low E string.
On piano, B♭m7♭5 has three black keys (B♭, D♭ and A♭) and one white key.
On ukulele the usual B♭m7♭5 shape is 3444, using four fingers.
Related chords
Take away the root and the other three notes form D♭m (D♭ F♭ A♭) — so you can think of B♭m7♭5 as D♭m with B♭ added underneath.
B♭m7♭5 contains exactly the same notes as C♯m6. Which name fits depends on which note is in the bass and what key you’re in.
Move a single note and B♭m7♭5 becomes a different chord: raise F♭ to F for B♭m7, drop the A♭ for B♭dim and lower A♭ to A𝄫 for B♭dim7.
Where you’ll hear it
Notice the F♭ in B♭m7♭5 (B♭ D♭ F♭ A♭): each note of the chord takes its own letter (B–D–F–A), so the diminished 5th has to be written F♭ rather than E — the same key on a piano, spelled to fit the chord.
