B diminished seventh (Bdim7) chord on piano

Diminished seventh chord (three stacked minor thirds) on B: the notes of the Bdim7 chord are B – D – F – A♭.

Root position: B3 – D4 – F4 – A♭4

What the Bdim7 chord sounds like

A diminished seventh is three stacked minor thirds, so it is symmetrical: four different roots give the same notes. A dramatic, tense passing chord.

Notes of the Bdim7 chord

Degree	Note	Interval from the root
1	B	root
3	D	minor third (3 semitones)
5	F	diminished fifth (6 semitones)
7	A♭	diminished seventh (9 semitones)

Root position and inversions

An inversion uses the same notes, with a different note at the bottom. When you change chords, choosing the nearest inversion keeps your hand almost still.

Root position

B3 – D4 – F4 – A♭4

1st inversion

D4 – F4 – A♭4 – B4

2nd inversion

F4 – A♭4 – B4 – D5

3rd inversion

A♭4 – B4 – D5 – F5

Which keys is it in?

The Bdim7 chord is built from the notes of these keys (for minor keys, both the natural and the harmonic minor are considered):

C minor: vii°7

Similar chords and substitutes

If Bdim7 is too hard, or you want a different colour in the same spot, these chords are worth a try.

Substitutes (by function)

G7 – an incomplete dominant: the diminished chord is the top of this seventh chord
C – where it leads (leading tone → root)

Same notes

Ddim7 – the same notes with a different root
Fdim7 – the same notes with a different root
A♭dim7 – the same notes with a different root

Simpler versions

Bdim – all 3 of its notes are in this chord

Frequently asked questions

What notes are in the Bdim7 chord?

B, D, F, A♭. The root is B; the intervals of the other notes from the root: minor third, diminished fifth, diminished seventh.

How do I play the Bdim7 chord on piano?

In root position, the right hand usually plays with fingers 1, 3 and 5 (thumb, middle finger, little finger); four-note chords with fingers 1, 2, 3 and 5. The left hand mirrors this: 5, 3, 1. In an inversion the top or bottom note moves to the other side, so your hand moves less when you change chords.

Why do some songbooks write H instead of B?

In German and Central European notation, H is the note B, and B is the note B♭. So a “B” chord in a German or Hungarian songbook is B♭ in English notation, and an “H” chord is B. Always check which notation your chord chart uses.