semicord

Ddim7 D diminished seventh chord

Notes
D F Ab Cb
Formula
1 b3 b5 bb7
Semitones
0 3 6 9 above the root
Other symbols
D°7, Do7

D to F is a minor third (3 semitones), F to Ab is a minor third (3 semitones), Ab to Cb is a minor third (3 semitones). Four notes each a minor third (3 semitones) apart, so the chord splits the octave into four equal parts and there are only three different diminished seventh chords. Every inversion is another diminished seventh named after its bass note: Fdim7, G#dim7 (also written Abdim7), Bdim7. The seventh is spelled Cb, a diminished seventh above D: one letter name above the major sixth B that sounds the same.

Ddim7 on the piano

C4D4E4F4G4A4Cb5C5D5E5F5G5A5B5C#4Eb4F#4Ab4Bb4C#5Eb5F#5Ab5Bb5C4DFAbCbC5

Root position from D4: D4, F4, Ab4, Cb5. Middle C is C4.

Ddim7 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 D as its lowest note.

4fr×DDAbAbCbCbFF×
A-shape, root on the A string at fret 5
x 5 6 4 6 x (low E to high e)
Sounds D3 Ab3 Cb4 F4
9frDD×CbCbFFAbAb×
E-shape, root on the E string at fret 10
10 x 9 10 9 x (low E to high e)
Sounds D3 Cb4 F4 Ab4

The E-shape and A-shape grips 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 seventh chords on other roots.

Inversions of Ddim7

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 positionD F Ab CbDdim7
1st inversionF Ab Cb DFdim7 (also read as Ddim7/F)
2nd inversionAb Cb D FG#dim7 (also written Abdim7; also read as Ddim7/Ab)
3rd inversionCb D F AbBdim7

Where Ddim7 fits

Ddim7 is vii°7 in Eb minor. Its four notes are evenly spaced, so the same keys are a diminished seventh on each of them, and the chord can lead a half step up from any of its notes: to a chord on Eb, F#, A or C. That is why it is the classic passing and pivot chord.