B9b5

B9b5 is B, D#, F, A and C#, a nine flat five. The shape this page opens on is written x21221, lowest string first.

Note by note. B is the root, D# is the major third, F is the flat fifth, A is the flat seventh and C# is the ninth.

Also written B9(b5), B9-5 or B9♭5. The same chord either way; which spelling you meet depends on who wrote the chart.

There are 5 common shapes for B9b5 on the guitar, and 22 derived voicings in 2 families.

One note away. Change a single note of B9b5 and you have B7b5 (with one note taken away), B9 (with one note moved), Baug9 (with one note moved) or B9#11 (with one note added).

The common shapes, written lowest string first: x21221, 767667, 7878x9, x-8-9-8-10-9, x-14-13-14-14-13.

Under the hand. None of the shapes for B9b5 uses an open string, so every one of them is movable; the lowest sits at the 1st fret. 3 of the 5 need a barre. Together they cover the neck from the 1st fret to the 14th.

Where it goes. B9b5 is a dominant with its tension raised, so it still points at E — 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. B9b5 has x2122x, 7676xx, x-x-9-8-10-9, x-14-13-14-14-x, x2x241, 7x786x, 7-6-7-10-x-x, x2126x.

Rootless. The root left to the bass player. Frees a finger for a tension. B9b5 has xx1221, x4324x, x6766x, x-x-11-10-10-11, x-x-13-14-14-13, x4x241, xx3645, x6x665.

Tensions. A shell of B9b5, root, third and seventh, leaves a string free, and the tones that belong over it are the b13 (G) and the 13 (G#).

What kind of chord this is. B9b5 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.