Chord · Bb Half-Diminished 7th (m7♭5)
B♭m7♭5 Chord
B♭m7♭5 is Bb, Db, Fb and Ab — the ii in a minor ii-V-i.
B♭m7♭5 on every instrument
The same 4 notes, 6 sets of hands. Open a diagram for alternate shapes, audio and the mistakes to avoid.
What B♭m7♭5 is made of
Bb Half-Diminished 7th (m7♭5) (Bb half-diminished 7th (m7♭5)) is built from the notes Bb, Db, Fb, Ab, with the interval pattern 1, b3, b5, b7. A common half-diminished 7th (m7♭5) chord across many styles.
Stack 1, b3, b5 and b7 on a root of B♭ and you get Bb, Db, Fb and Ab. That interval recipe is what makes the chord a half diminished seventh chord — move the same shape to another root and the character travels with it, which is why Cm7♭5 sounds like a transposed B♭m7♭5.
Half-Diminished 7th (m7♭5): The ii in a minor ii-V-i.
Spelling: the notes above are written the way a score would write them, not simplified to the nearest piano key. That is why this chord is spelled with B♭ rather than its enharmonic equivalent.
Keys that contain B♭m7♭5
All 4 notes sit inside the scale of 4 keys. The roman numeral marks the degree the chord is rooted on.
Other chords on B♭
Same root, different colour.
The same half diminished seventh shape, moved
The identical interval recipe, built on other roots.
Questions people ask about Bbm7b5
- What notes are in the Bbm7b5 chord?
- Bbm7b5 is made of Bb, Db, Fb and Ab — the 1, b3, b5 and b7 degrees of a half diminished seventh chord built on Bb.
- What keys use the Bbm7b5 chord?
- Every note of Bbm7b5 belongs to 4 keys: B Major (vii°), Cb Major (vii°), G# Minor (ii°), Ab Minor (ii°). The roman numeral is the scale degree the chord is rooted on.
- How do you play Bbm7b5 on guitar and piano?
- This page shows Bbm7b5 on guitar, piano, ukulele, bass, mandolin and banjo — 9 voicings in total. Each diagram links to the full instrument page with alternate shapes, audio and common mistakes.
- Is Bbm7b5 the same as A#m7b5?
- Yes. Bbm7b5 and A#m7b5 are enharmonic — identical pitches written two different ways. Which spelling you use depends on the key you are in; Bbm7b5 is the spelling this site treats as canonical.
Learn the theory behind it
Why B♭m7♭5 behaves the way it does — the guides that explain the chord instead of just spelling it.