B flat Diminished Chord (B♭dim)

1Composition: what it contains

B♭ – D♭ – F♭

Symbol

B♭dim

Also written

B♭dim, B♭°, B♭m♭5, B♭mi(♭5)

Formula

1 ♭3 ♭5

Same sound as

A♯dim

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 · B♭dim/D♭ · D♭ – F♭ – B♭ Play
• Inversion 2 · B♭dim/F♭ · F♭ – B♭ – D♭ Play

Scales to play over B♭dim

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

Where it appears (keys and Roman numerals)

• vii° – Key of B Major
• vii° – Key of C flat Major
• ii° – Key of G sharp Minor
• ii° – Key of A flat Minor

7Other presentations available

The same chord from every note

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

Other chords on B♭

B♭ B♭m B♭aug B♭sus2 B♭sus4 B♭5 B♭6 B♭m6 B♭7 B♭maj7 B♭m7 B♭m7♭5 B♭dim7 B♭m(maj7) B♭7sus4 B♭add9 B♭m(add9) B♭6/9 B♭9 B♭maj9 B♭m9 B♭11 B♭m11 B♭13 B♭7♭9 B♭7♯9 B♭7♯5 B♭7♭5