C9 keeps the dominant notes of and includes the : C, E, G, Bb and D. A plain 9 chord includes the flat 7th.
The major 3rd and flat 7th still identify the dominant. The 9th can carry the upper line into the next chord.
Also written Cdom9 or C dominant 9.
Drop the third voice from the top an octave instead. The wider gap skips a string, so the muted string is part of the shape.
That result, 3–R–5–7, is the shape usually meant by drop 3. Named by its bass note, as the inversions are here, it is the 1st inversion.
More familiar jazz shapes are drop 3 than drop 2.
C9 goes wherever a dominant seventh goes; the ninth is only an added colour. When the chord resolves, the ninth does what the seventh does and falls a step.
Listen for: The ninth falls a whole step to the fifth of the I. On the plain seventh chord that string plays the root, which just holds.
In which keys. Every note of C9 belongs to D minor and F major.
Contains C9 and adds eleventh and thirteenth.
Adds sharp eleventh and thirteenth, for a dominant sharp-eleventh color.
The common shapes and the derived voicings come from different places, and both are explained in how this site is built.
Shows each chord the way this style would voice it, and marks which of its alternatives belong to the idiom.