Bbm7b5

Bbm7b5 is Bb, Db, Fb and Ab, a half-diminished seventh. The shape this page opens on is written x1212x, lowest string first.

Also written Bbø, Bbø7, Bbm7-5, Bbm7(b5) or Bb half diminished. The same chord either way; which spelling you meet depends on who wrote the chart.

There are 8 common shapes for Bbm7b5 on the guitar, and 28 derived voicings in 3 families.

In which keys. Every note of Bbm7b5 belongs to Ab minor (the ii°) and B major (the vii°).

The common shapes, written lowest string first: x1212x, xx2324, 6xx654, 6x665x, 678696, xx8999, x-13-11-13-11-12, x-13-14-13-14-x.

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. Bbm7b5 has x1x120, 6x665x, x-13-x-13-14-12, x1665x, 6469xx, 6-11-11-9-x-x.

Drop 2. A close-position chord with the second voice from the top lowered an octave. Sits on four adjacent strings. Bbm7b5 has x1212x, xx2324, 4423xx, xx6656, 6766xx, xx8999, x-11-11-9-11-x, 12-13-11-13-x-x.

Drop 3. The third voice from the top lowered an octave. The dropped voice becomes the bass, which is why a string is skipped. Bbm7b5 has x1x120, 4x232x, x4x354, 6x665x, x7x696, 9x899x, x-11-x-9-11-9, 12-x-11-13-11-x.

Tensions. A shell of Bbm7b5, root, third and seventh, leaves a string free, and the tones that belong over it are the 11 (Eb) and the b13 (Gb).

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