C#dim guitar chord
An open string left ringing against a fretted grip. Because it costs no finger, it sounds a note the closed shape has none left for -- a tension on top, or a pedal root underneath. Either a familiar grip with open strings added, or a shape so sparse the open strings carry the chord. These belong to their key rather than to a shape, so D, A, G and E have many and Eb a handful.
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About C#dim — open string voicings
C#dim is C#, E and G — C#m with the fifth lowered as well.
It sounds compressed and unstable in every direction. Rarely a destination; it is where a line passes through on the way somewhere.
C#dim notes and formula
| C# | E | G |
|---|---|---|
| 1 | ♭3 | ♭5 |
Unstable — it does not sit still.
Also written C#°, C#o or C# diminished. The same chord either way; which spelling you meet depends on who wrote the chart.
How to play C#dim
An open string left ringing against a fretted grip. It costs no finger, so it can sound a note the closed shape has none left for: a tension on top, or a pedal root underneath.
These belong to their key rather than to a shape: they cannot be moved up the neck. D, A, G and E have many; E♭ has a handful.
C#dim has 6 of them, on strings 6-5-4-3-2, strings 6-5-4-3-2-1, the bottom four strings, strings 6-4-3-2 and the top four strings, from the 2nd fret up to the 7th — all in one inversion, so the bass note never moves. The one to learn first is the E shape at the 2nd fret, which is the easiest grip here.
Start with x42x23 — down at the nut. None of the shapes for C#dim uses an open string, so every one of them is movable; the lowest sits at the 2nd fret. None of them needs a barre. Together they cover the neck from the 2nd fret to the 12th.
| Frets | Where | Bass | Top | Hand |
|---|---|---|---|---|
| x42x23 | 2nd fret | C#, root position | G | all fretted |
| x4565x | 4th fret | C#, root position | E | all fretted |
| 97x98x | 7th fret | C#, root position | G | all fretted |
| x-x-11-12-x-12 | 11th fret | C#, root position | E | all fretted |
The same notes rebuilt from scratch give 48 triad voicings, each on its own page.
Tensions. A shell of C#dim, root, third and seventh, leaves a string free, and the tones that belong over it are the 11 (F#) and the b13 (A).
How to use C#dim
In which keys. Every note of C#dim belongs to D major (the vii°, the leading tone) and B minor (the ii°, the supertonic).
What to play over C#dim
Every note of C#dim is in C# blues, C# locrian, C# altered, C# diminished and C# half-whole diminished.
Chords near C#dim
Change one note of C#dim and you have C#m (the flat fifth becomes a fifth), C#dim7 (add the sixth), C#m7b5 (add the flat seventh) or C#mMaj7b5 (add the major seventh).
C#dim is a diminished chord — root, minor third, flat fifth. Diminished and half-diminished chords on every root.
On C#dim’s sound and use this page follows Stefan Kostka, Dorothy Payne & Byron Almén, Tonal Harmony (McGraw-Hill, 8th ed., 2018). The shapes and the derived voicings come from different places, and both are explained in where the chords and the theory come from.