The B♭ Half Diminished chord is a four-note chord made up of B♭, D♭, F♭, and A♭. It is built from a root, minor third, diminished fifth, and minor seventh.
Construction
B♭ Half Diminished = Root + Minor 3rd + Diminished 5th + Minor 7th = B♭ · D♭ · F♭ · A♭
| Note | Interval | Degree |
|---|---|---|
| B♭ | Root | 1 |
| D♭ | Minor 3rd | ♭3 |
| F♭ | Diminished 5th | ♭5 |
| A♭ | Minor 7th | ♭7 |
B♭ Half Diminished Inversions
| Position | Notes |
|---|---|
| Root Position | B♭ – D♭ – F♭ – A♭ |
| 1st Inversion | D♭ – F♭ – A♭ – B♭ |
| 2nd Inversion | F♭ – A♭ – B♭ – D♭ |
| 3rd Inversion | A♭ – B♭ – D♭ – F♭ |
Key Signature
A Half Diminished chord is built from symmetrical or ambiguous intervals, so it doesn’t belong to a single key and has no key signature of its own.
How B♭ Half Diminished functions in a key
The same chord takes on a different harmonic role depending on the key it appears in. Here is where B♭ Half Diminished sits diatonically across the common keys:
- In C♭ major, B♭ Half Diminished is the vii° chord — the dominant.
- In A♭ minor, B♭ Half Diminished is the ii° chord — a predominant.
Same Notes, Other Names
The notes B♭ – D♭ – F♭ – A♭ aren’t exclusive to this chord. Depending on which note is the bass and how the chord functions, the same pitches also spell:
B♭ Half Diminished — Frequently Asked Questions
What is the B♭ Half Diminished chord on piano?
The B♭ Half Diminished chord contains the notes B♭ – D♭ – F♭ – A♭. On piano, play these notes together to sound the chord.
What notes are in the Bb Half Diminished chord?
Bbm7b5 contains: Bb, Db, Fb, Ab. Diminished triad with minor seventh.
How does Bbm7b5 differ from Bbdim7?
Minor seventh (Ab) vs diminished seventh (Abb/G).
How is Bbm7b5 used?
ii chord in Ab minor.
What songs use Half Diminished?
Jazz minor-key harmony.
How does Bbm7b5 differ from Bbm7?
Flatted fifth (Fb vs F).
Is Bbm7b5 the same as Dbm6?
Same notes, different root.