C9

C9 is C, E, G, Bb and D, a dominant ninth. The shape this page opens on is written x32030, lowest string first.

Also written Cdom9 or C dominant 9. The same chord either way; which spelling you meet depends on who wrote the chart.

There are 10 common shapes for C9 on the guitar, and 50 derived voicings in 5 families.

In which keys. Every note of C9 belongs to D minor (the ♭VII) and F major (the V).

The common shapes, written lowest string first: x32030, x32333, x55556, 855756, 8787xx, 8-10-8-7-8-10, 8-10-8-9-8-10, x-x-10-9-11-10, 12-x-10-12-11-10, x-15-14-15-15-15.

Shell. Root, third and seventh: the guide tones fix the quality, so the fifth is dropped. That is what leaves a string free, so pick a tension to put on top. C9 has x3233x, 8787xx, x-x-10-9-11-10, x-15-14-15-15-x.

Drop 2. A close-position chord with the second voice from the top lowered an octave. Sits on four adjacent strings. C9 has xx0310, x3233x, 0303xx, 8787xx, x-x-10-9-11-10, x-15-14-15-15-x, xx2536, 6525xx.

Drop 3. The third voice from the top lowered an octave. The dropped voice becomes the bass, which is why a string is skipped. C9 has 0x031x, 6x253x, x3x330, x5x556, 8x875x, x-7-x-7-11-8, 10-x-10-9-11-x, x-13-x-9-13-10.

Rootless. The root left to the bass player. Frees a finger for a tension. C9 has x1203x, xx2333, x5535x, xx5756, x7878x, x-x-8-9-8-10, x-x-12-12-11-12, x-x-14-15-15-15.

Open string. 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. C9 has 005756, 0x0076, 6x0070, 0303xx, xx0056, 6700xx.

Tensions. A shell of C9, root, third and seventh, leaves a string free, and the tones that belong over it are the #11 (F#), the b13 (Ab) and the 13 (A).

The common shapes and the derived voicings come from different places, and both are explained in where the chords and the theory come from.