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 B Diminished 7th chord?
The B Diminished 7th chord (Bdim7) contains four notes: B (root), D (minor third), F (diminished fifth), and Ab (diminished seventh). All four notes are spaced exactly 3 semitones apart.
How does B Diminished 7th differ from B Diminished?
B Diminished is a three-note triad (B, D, F). B Diminished 7th adds Ab as the diminished seventh, completing the symmetrical four-note structure and maximising harmonic tension.
Why is the Diminished 7th chord symmetrical?
Bdim7 contains the same pitches as Ddim7, Fdim7, and Abdim7 — all inversions of the same four notes (B, D, F, Ab). Only three unique dim7 chords exist.
How is B Diminished 7th used in music?
Bdim7 is the vii°7 chord in C Major — the most common key in music. It resolves up by half step to C Major and appears constantly in classical cadences, jazz turnarounds, and pop as a leading-tone chord.
What songs use Diminished 7th chords?
Diminished 7th chords appear in Michelle (Beatles), throughout Chopin and Beethoven, and in jazz standards. Bdim7 is one of the most frequently encountered dim7 chords because C Major is the most common key.
How many unique Diminished 7th chords exist?
Only three. Bdim7 shares its notes with Ddim7, Fdim7, and Abdim7. The other two groups are Cdim7 and Dbdim7.