semicord

Gdim G diminished chord

Notes
G Bb Db
Formula
1 b3 b5
Semitones
0 3 6 above the root
Other symbols
G°, Gm(b5)

G to Bb is a minor third (3 semitones), Bb to Db is a minor third (3 semitones). Two minor thirds stacked, so G to Db is a tritone (6 semitones) instead of a perfect fifth. The four-note Gdim7 and Gm7b5 grow from it by adding a note on top.

Gdim on the piano

C4D4E4F4G4A4B4C5D5E5F5G5A5B5C#4Eb4F#4Ab4Bb4Db5Eb5F#5Ab5Bb5C4GBbC5Db

Root position from G4: G4, Bb4, Db5. Middle C is C4.

Gdim 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 G as its lowest note.

GGDbDbGGBbBb××
E-shape barre, root on the E string at fret 3
3 4 5 3 x x (low E to high e)
Sounds G2 Db3 G3 Bb3
10fr×GGDbDbGGBbBb×
A-shape barre, root on the A string at fret 10
x 10 11 12 11 x (low E to high e)
Sounds G3 Db4 G4 Bb4

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 Gdim

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 positionG Bb DbGdim
1st inversionBb Db GGdim/Bb
2nd inversionDb G BbGdim/Db

Where Gdim fits

Gdim is vii° in Ab major, ii° in F minor, vii° in Ab minor. Its root G is the leading tone of Ab: a half step below the tonic, so the chord usually moves up to it.