C7b9

C7b9 is C, E, G, Bb and Db, a seven flat nine. The shape this page opens on is written x32323, lowest string first.

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

Also written C7(b9), C7-9 or C7♭9. The same chord either way; which spelling you meet depends on who wrote the chart.

There are 6 common shapes for C7b9 on the guitar, and 42 derived voicings in 5 families.

One note away. Change a single note of C7b9 and you have C7 (with one note taken away), C7/G (with one note taken away), Calt (with one note moved), C9 (with one note moved) or C7#9 (with one note moved).

The common shapes, written lowest string first: x32323, 8786xx, xx8989, 8-10-8-9-8-9, x-x-10-9-11-9, x-15-14-15-14-15.

Under the hand. None of the shapes for C7b9 uses an open string, so every one of them is movable; the lowest sits at the 2nd fret. 3 of the 6 need a barre. Together they cover the neck from the 2nd fret to the 15th.

Where it goes. C7b9 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. C7b9 has x3232x, 8786xx, x-x-10-9-11-9, x-15-14-15-14-x.

Drop 2. A close-position chord with the second voice from the top lowered an octave. Sits on four adjacent strings. C7b9 has x3232x, 8786xx, x-x-10-9-11-9, x-15-14-15-14-x, xx2526, 6425xx, x4855x, xx8658.

Drop 3. The third voice from the top lowered an octave. The dropped voice becomes the bass, which is why a string is skipped. C7b9 has 6x252x, x3x320, x4x556, 8x865x, 9-x-10-9-11-x, x-13-x-9-13-9, 12-x-11-15-13-x, x-15-x-15-14-12.

Rootless. The root left to the bass player. Frees a finger for a tension. C7b9 has x1202x, xx2323, x4535x, xx5656, x7868x, xx8989, x-10-11-9-11-x, x-x-11-12-11-12.

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. C7b9 has 005656.

Tensions. A shell of C7b9, 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).

What kind of chord this is. C7b9 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.