C13

C13 is C, E, G, Bb, D and A, a dominant thirteenth. The shape this page opens on is written x32355, lowest string first.

Note by note. C is the root, E is the major third, G is the fifth, Bb is the flat seventh, D is the ninth and A is the thirteenth.

Also written Cdom13 or C dominant 13. The same chord either way; which spelling you meet depends on who wrote the chart.

There are 7 common shapes for C13 on the guitar, and 52 derived voicings in 5 families.

One note away. Change a single note of C13 and you have Cmaj13 (with one note moved), C69 (with one note taken away), C9 (with one note taken away) or C9#11 (with one note moved).

In which keys. Every note of C13 belongs to D minor (the ♭VII) and F major (the V).

The common shapes, written lowest string first: x32355, x32335, 333355, 857556, 877786, 8-8-8-9-10-10, 8-10-8-9-10-8.

Under the hand. None of the shapes for C13 uses an open string, so every one of them is movable; the lowest sits at the 2nd fret. 6 of the 7 need a barre. Together they cover the neck from the 2nd fret to the 10th.

Where it goes. C13 is the V of F, and that is where it goes if it goes anywhere: the third and the flat seventh are a tritone apart, and both resolve by a semitone into F.

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. C13 has x3x355, 8-x-8-9-10-x.

Drop 2. A close-position chord with the second voice from the top lowered an octave. Sits on four adjacent strings. C13 has x1221x, xx7556, 6775xx, x-x-8-9-10-8, x-13-14-14-13-x, xx2315, 5323xx, x3735x.

Drop 3. The third voice from the top lowered an octave. The dropped voice becomes the bass, which is why a string is skipped. C13 has 5x231x, x1x210, x3x355, 6x755x, x-12-x-9-11-8, 8-x-8-9-10-x, 12-x-10-14-11-x, x-13-x-14-13-12.

Rootless. The root left to the bass player. Frees a finger for a tension. C13 has x1223x, xx5355, xx7756, x-x-8-9-10-10, x-10-8-9-10-x, x-13-14-14-15-x, x1x230, x1x253.

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. C13 has 030355, x00056, 0003xx, x0035x.

Tensions. A shell of C13, root, third and seventh, leaves a string free, and the tones that belong over it are the #11 (F#).

What kind of chord this is. C13 is a dominant chord — root, major third, fifth, minor seventh. dominant seventh chords on every root, and what they are for.

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