C9 chord on cavaquinho
C9 is the dominant ninth chord: C, E, G, Bb and D (1–3–5–b7–9). On cavaquinho, the diagram shape is 2 3 1 0, with E in the bass.
On the cavaquinho, four steel strings tuned D–G–B–D pack the chord into a small, bright space — every finger counts. In this C9 voicing the bass is E and the shape runs from fret 1 to 3, ringing 1 open string. Because this instrument has fewer strings than C9 has notes, one note, usually the fifth, is normally dropped without losing the chord's identity. Its four steel strings give a bright, sharp attack that cuts through the mix and drives the beat.
Notes and formula of C9
Notes in C9: C – E – G – Bb – DFormula: 1 – 3 – 5 – b7 – 9In 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
Blues, funk, choro and broader dominants.
See also
Part of the Extended family.