C9b5

C9b5 is C, E, Gb, Bb and D, a nine flat five. The shape this page opens on is written x32332, lowest string first.

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

Also written C9(b5), C9-5 or C9♭5. The same chord either way; which spelling you meet depends on who wrote the chart.

There are 6 common shapes for C9b5 on the guitar, and 24 derived voicings in 3 families.

One note away. Change a single note of C9b5 and you have C7b5 (with one note taken away), C9 (with one note moved), Caug9 (with one note moved) or C9#11 (with one note added).

The common shapes, written lowest string first: x32332, x34330, 878778, 8-9-8-9-x-10, x-9-10-9-11-10, x-15-14-15-15-14.

Under the hand. 1 of the 6 shapes here sits in open position, and the first uses 1 open string with 1 left unplayed. 4 of the 6 need a barre. Together they cover the neck from the 2nd fret to the 15th.

Where it goes. C9b5 is a dominant with its tension raised, so it still points at F — harder than a plain seventh does, because the altered tones sit a semitone from where they are going.

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. C9b5 has x3233x, 8787xx, x-x-10-9-11-10, x-15-14-15-15-x, x3x352, 8x897x, 8-7-8-11-x-x, x3237x.

Rootless. The root left to the bass player. Frees a finger for a tension. C9b5 has xx2332, x5435x, x7877x, x-x-12-11-11-12, x-x-14-15-15-14, x5x352, xx4756, x7x776.

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. C9b5 has 004756, 030352.

Tensions. A shell of C9b5, root, third and seventh, leaves a string free, and the tones that belong over it are the b13 (Ab) and the 13 (A).

What kind of chord this is. C9b5 is an altered chord — a dominant seventh with its fifth or ninth moved. altered dominant 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.