The B♭ Diminished 7th 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 diminished seventh.
Construction
B♭ Diminished 7th = Root + Minor 3rd + Diminished 5th + Major 6th = B♭ · D♭ · F♭ · A♭♭
| Note | Interval | Degree |
|---|---|---|
| B♭ | Root | 1 |
| D♭ | Minor 3rd | ♭3 |
| F♭ | Diminished 5th | ♭5 |
| A♭♭ | Major 6th | 6 |
B♭ Diminished 7th 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 Diminished 7th 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.
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 the following:
B♭ Diminished 7th — Frequently Asked Questions
What is the B♭ Diminished 7th chord on piano?
The B♭ Diminished 7th chord contains the notes B♭ – D♭ – F♭ – A♭♭. On piano, play these notes together to sound the chord.
What notes are in the Bb Diminished 7th chord?
The Bb Diminished 7th chord (Bbdim7) contains four notes: Bb (root), Db (minor third), Fb (diminished fifth, enharmonically E), and Abb (diminished seventh, enharmonically G). All four notes are spaced exactly 3 semitones apart.
How does Bb Diminished 7th differ from Bb Diminished?
Bb Diminished is a three-note triad (Bb, Db, Fb). Bb Diminished 7th adds Abb/G as the diminished seventh, completing the symmetrical structure.
Why is the Diminished 7th chord symmetrical?
Bbdim7 contains the same pitches as Dbdim7, Edim7, and Gdim7 — all inversions of the same four notes (Bb, Db, E, G). Only three unique dim7 chords exist.
How is Bb Diminished 7th used in music?
Bbdim7 functions as the vii°7 of B/Cb, resolving up by half step to B Major. It works as a chromatic passing chord in many contexts and appears in jazz, classical, and gospel music.
What songs use Diminished 7th chords?
Diminished 7th chords appear in Michelle (Beatles), throughout Chopin and Beethoven, and in jazz standards for chromatic voice leading. Film and musical theatre scores use dim7 for dramatic tension.
How many unique Diminished 7th chords exist?
Only three. Bbdim7 shares its notes with Dbdim7, Edim7, and Gdim7. The other two groups are Cdim7 and Ddim7.