B Diminished Chord (Bdim)

1Composition: what it contains

B – D – F

Symbol

Bdim

Also written

Bdim, B°, Bm♭5, Bmi(♭5)

Formula

1 ♭3 ♭5

2Appearance: diagrams and sound

On the guitar

On the ukulele

On the piano

On the staff

On bass and as an arpeggio

3Indications: what it is used for

The vii° chord of a major key and the ii° chord of a minor key are diminished triads. It works as a leading-tone chord resolving to the tonic (vii°–I), as a passing chord between two diatonic chords (for example between I and ii, or IV and V), and as an incomplete dominant seventh: the vii° triad contains the 3, 5 and 7 of V7. Classical, jazz, gospel and film music use it for tension and chromatic movement in the bass.

4Dosage: how to practise it

On piano, play the triad in all inversions at 60 BPM, then practise vii°6–I resolutions with smooth voice leading (the diminished fifth contracting to a third). On guitar, learn the compact three-string shapes on the top strings and the shape rooted on the fifth string. Practise the passing progression I–♯I°–ii–V slowly, then at 80–100 BPM. Arpeggiate 1-♭3-♭5 on bass. Five minutes a day is enough once the shapes are known.

5Warnings and common mistakes

Do not confuse the triad (dim) with the diminished seventh chord (dim7 or °7) or the half-diminished seventh (m7♭5 or ø7): many charts write 'dim' when they mean the four-note dim7, so check the style. The diminished fifth is not a perfect fifth; on guitar, power-chord habits make players play the wrong fifth. In root position the triad can sound harsh; first inversion is the most common classical voicing.

6Interactions with chords, scales and keys

Inversions

• Inversion 1 · Bdim/D · D – F – B Play
• Inversion 2 · Bdim/F · F – B – D Play

Scales to play over Bdim

• B Locrian Mode
• B Blues Scale
• B Half-Whole Diminished Scale
• B Whole-Half Diminished Scale
• B Hungarian Minor Scale
• B Altered Scale

Where it appears (keys and Roman numerals)

• vii° – Key of C Major
• ii° – Key of A Minor

7Other presentations available

The same chord from every note

Cdim C♯dim Ddim E♭dim Edim Fdim F♯dim Gdim A♭dim Adim B♭dim

Other chords on B

B Bm Baug Bsus2 Bsus4 B5 B6 Bm6 B7 Bmaj7 Bm7 Bm7♭5 Bdim7 Bm(maj7) B7sus4 Badd9 Bm(add9) B6/9 B9 Bmaj9 Bm9 B11 Bm11 B13 B7♭9 B7♯9 B7♯5 B7♭5