Diminished Chord
A diminished chord, also called a diminished triad, contains a root, minor third and diminished fifth. C diminished is C, E flat and G flat. The root and flat fifth form a tritone, and the chord commonly acts as a leading-tone or passing harmony whose destination clarifies its function.
- 1-flat 3-flat 5
- two minor thirds
- tritone from root to flat 5
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Which notes are in C diminished?
Use the formula 1-flat 3-flat 5:
- C: root
- E flat: minor third
- G flat: diminished fifth
Symbols include Cdim and C with a small degree circle. C diminished has three notes; Cdim7 adds a diminished seventh.
How do you build it?
Start with C minor, C-E flat-G, and lower G to G flat.
The adjacent intervals C-E flat and E-flat-G flat are both minor thirds.
The outer interval C-G flat spans six semitones and is a diminished fifth, one spelling of the tritone.
Where does it occur in a major key?
A diminished triad occurs diatonically on degree vii.
In C major, B-D-F forms B diminished.
As a leading-tone chord, B rises to C and F commonly falls to E. D may move to C or E according to the voicing.
Does every diminished triad resolve upward by semitone?
No. B diminished commonly resolves to C because B is the leading tone in that key.
C diminished could resolve to D-flat major when C functions as its leading tone, or act as part of another passing progression.
Identify the key, spelling and destination. The chord type alone does not specify one root motion.
How is it related to G7?
G7 contains G-B-D-F. B diminished contains B-D-F.
The diminished triad supplies the third, fifth and seventh of G7 while omitting its root G.
This shared guide-tone structure explains why vii diminished and V7 can both lead to C.
What is the difference from C minor?
C minor is C-E flat-G. C diminished lowers G to G flat.
That one semitone changes the perfect fifth into a diminished fifth and introduces the tritone C-G flat.
Keep C and E flat fixed while comparing the two chords.
What is the difference from Cm7 flat 5 and Cdim7?
C diminished contains C-E flat-G flat.
Cm7 flat 5 adds B flat, a minor seventh. Cdim7 adds B double flat, a diminished seventh.
The seventh determines half-diminished or fully diminished structure. Spell it from C instead of choosing only by piano key.
Which scales contain it?
C diminished appears as degree vii in D-flat major.
It can also occur on degree ii of B-flat natural minor and inside harmonic-minor-related harmony.
The whole-half diminished scale contains C-E flat-G flat plus additional notes, but a three-note chord does not determine one unique scale.
How do inversions work?
Root position is C-E flat-G flat. First inversion places E flat in the bass; second inversion places G flat in the bass.
The chord remains C diminished when context preserves C as root.
An inversion can resemble another root interpretation, so use spelling and resolution to confirm the analysis.
How should you voice it?
Keep the tritone clear and avoid unnecessary low-register density.
Double the note whose voice leading makes sense in the destination chord. In strict tonal writing, doubling the leading tone can create two voices that both demand the same resolution.
For keyboard or guitar, choose a voicing that lets each note move by step into the next harmony.
How should you practice it?
Build C minor and lower G to G flat.
Play B-D-F, then resolve B-C and F-E while choosing D-C or D-E.
Add B flat for Cm7 flat 5 and B double flat for Cdim7, naming the different seventh each time.