Sevenths
B♭ diminished 7th chord
Symmetrical and very tense — every note is a minor 3rd apart.
B♭dim7 is the vii°7 chord in B minor.
- Notes
- B♭D♭F♭A𝄫
- Formula
- 1♭3♭5𝄫7
- Built from
- root · minor 3rd · diminished 5th · diminished 7th
How to play B♭dim7
About the B♭ diminished 7th chord
Playing it
On guitar, B♭dim7 has an open-position shape, x12020, using three fingers alongside the open strings. Don’t strum the low E string.
On piano, B♭dim7 has two black keys (B♭ and D♭) and two white keys.
On ukulele the usual B♭dim7 shape is 0101, using two fingers.
Related chords
Take away the root and the other three notes form D♭dim (D♭ F♭ A𝄫) — so you can think of B♭dim7 as D♭dim with B♭ added underneath.
B♭dim7 is symmetrical — its notes are evenly spaced — so C♯dim7, Edim7 and Gdim7 contain exactly the same notes. There are only three different-sounding diminished 7th chords in all.
Move a single note and B♭dim7 becomes a different chord: drop the A𝄫 for B♭dim, raise F♭ to F for B♭m6 and raise A𝄫 to A♭ for B♭m7♭5.
Where you’ll hear it
Notice the F♭ in B♭dim7 (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.
