E Diminished
dim
0 - 3 - 6Root + minor 3rd + diminished 5th
About E Diminished
E diminished is a symmetrical chord — E, G, B♭ — with a tritone at its centre and no settled root. On guitar it appears almost exclusively as a passing chord, where its instability moves a bass line by a semitone and the ear reads it as motion rather than harmony.
The notes
E, G, B♭. Two stacked minor thirds. Because the intervals are equal, inverting the chord produces the same shape, and any of its notes can act as the root.
Add a C♯ below and the chord becomes C♯7♭9 — the relationship that makes diminished shapes so useful in jazz, where one grip covers four dominants.
How it is used
Between two chords a tone apart, filling the gap chromatically. In the key of A minor it links Am and F♯ diminished in a descending line; in G major it connects Em and D.
On guitar it is usually voiced on three or four strings only. The full symmetrical shape adds difficulty without adding much sound, and the chord rarely lasts more than a beat.
The shape also repeats every three frets, because the chord is symmetrical: the grip at the second fret and the grip at the fifth contain the same notes in a different order. That property is what makes diminished shapes so quick to move.
Where it shows up
As the vii of F major in strict theory, and everywhere else as a connector. Early jazz and silent-film accompaniment used it constantly, and the association has stuck.
It also appears as a rootless dominant in modern arranging, where a guitarist plays the diminished shape and the bass supplies a root a semitone below the expected one.