semicord

Bdim B diminished chord

Notes
B D F
Formula
1 b3 b5
Semitones
0 3 6 above the root
Other symbols
B°, Bm(b5)

B to D is a minor third (3 semitones), D to F is a minor third (3 semitones). Two minor thirds stacked, so B to F is a tritone (6 semitones) instead of a perfect fifth. The four-note Bdim7 and Bm7b5 grow from it by adding a note on top.

Bdim on the piano

C4D4E4F4G4A4B4C5D5E5F5G5A5B5C#4Eb4F#4Ab4Bb4C#5Eb5F#5Ab5Bb5C4BC5DF

Root position from B4: B4, D5, F5. Middle C is C4.

Bdim on the guitar

Standard tuning (E A D G B E). Strings run low E on the left to high e on the right, frets downwards; × is a muted string, ○ an open string, and each dot shows the note it sounds, with the root in blue-green. Every shape below has B as its lowest note.

×BBFFBBDD×
A-shape barre, root on the A string at fret 2
x 2 3 4 3 x (low E to high e)
Sounds B2 F3 B3 D4
7frBBFFBBDD××
E-shape barre, root on the E string at fret 7
7 8 9 7 x x (low E to high e)
Sounds B2 F3 B3 D4

The barre shapes are movable: an E-shape chord's root is the note under your first finger on the low E string, an A-shape chord's root is the note on the A string. Slide the same grip up or down to play diminished chords on other roots.

Inversions of Bdim

An inversion puts a note other than the root in the bass. The name is what semicord's chord finder calls those notes played bottom to top; a slash name like C/E means a C chord with E in the bass.

PositionNotes, bass firstNamedListen
Root positionB D FBdim
1st inversionD F BBdim/D
2nd inversionF B DBdim/F

Where Bdim fits

Bdim is vii° in C major, ii° in A minor, vii° in C minor. Its root B is the leading tone of C: a half step below the tonic, so the chord usually moves up to it.