Cdim7 chord on electric guitar
Cdim7 is the diminished seventh chord: C, Eb, Gb and A (1–b3–b5–bb7). On electric guitar, the diagram shape is x 3 4 2 4 x, with C in the bass.
On the electric guitar a chord needs only a few clear notes — the amp sustains them and fills the space, so you mute the strings you are not playing and let the tone carry the rest. In this Cdim7 voicing the bass is C and the shape runs from fret 2 to 4. Plugged into an amp, each chord sustains for as long as you hold it, and the tone — clean or driven — shapes the whole sound.
Notes and formula of Cdim7
Notes in Cdim7: C – Eb – Gb – AFormula: 1 – b3 – b5 – bb7In the formula, the numbers count steps of the major scale starting from the note that names the chord; "b" lowers a half step, "#" raises one — and a slash names the bass note.
Where to use it
Between two neighbouring chords it acts as a half-step stair: in C → C#° → DmDmDmDm it is the little step that pushes the music forward. In practice it is a passing chord — you barely notice it, but you feel the motion.
See also
Part of the Sevenths family.