Bbm7b5 guitar chord
The third voice from the top lowered an octave. The dropped voice becomes the bass, which is why a string is skipped.
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About Bbm7b5 — drop 3 voicings
Bbm7b5 is Bb, Db, Fb and Ab — Bbm7 with the fifth lowered a semitone.
It sounds hollow, and unmistakably going somewhere. Almost always the first chord of a minor ii–V–i, so it walks straight into an altered dominant.
Bbm7b5 notes and formula
| Bb | Db | Fb | Ab |
|---|---|---|---|
| 1 | ♭3 | ♭5 | ♭7 |
Pre-dominant — the ii of a minor key.
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.
How to play Bbm7b5
The same operation one voice further down: the third voice from the top falls an octave and becomes the bass.
That leaves a bigger hole under the top three notes, so a string gets skipped: the muted string in the middle is the shape, not a mistake.
Bbm7b5 has 9 of them, on strings 5-3-2-1 and strings 6-4-3-2, from open position up to the 12th — every inversion the chord has: Bb in the bass, Db in the bass, Fb in the bass and Ab in the bass. The one to learn first is the Bb shape at the nut.
5 of them sit on strings 5-3-2-1, so you can run the inversions up one set without changing strings — which is the whole reason to learn them as a family rather than as separate grips.
Start with x1212x — no barre and down at the nut. None of the shapes for Bbm7b5 uses an open string, so every one of them is movable; the lowest sits at the 1st fret. 3 of the 8 need a barre. Together they cover the neck from the 1st fret to the 14th.
| Frets | Where | Bass | Top | Hand |
|---|---|---|---|---|
| x1212x | 1st fret | Bb, root position | Db | all fretted |
| xx2324 | 2nd fret | Fb, 2nd inversion | Ab | all fretted |
| 6xx654 | 4th fret | Bb, root position | Ab | all fretted |
| 6x665x | 5th fret | Bb, root position | Fb | barred |
| 678696 | 6th fret | Bb, root position | Bb | barred |
| xx8999 | 8th fret | Bb, root position | Db | barred |
| x-13-11-13-11-12 | 11th fret | Bb, root position | Fb | all fretted |
| x-13-14-13-14-x | 13th fret | Bb, root position | Db | all fretted |
The same notes rebuilt from scratch give 6 shell and 13 drop 2 voicings, each on its own page.
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).
How to use Bbm7b5
Bbm7b5 is the ii of Ab minor, which is where it is nearly always found: half-diminished, then an altered dominant, then the minor tonic.
In which keys. Every note of Bbm7b5 belongs to Ab minor (the ii°, the supertonic) and B major (the vii°, the leading tone).
What to play over Bbm7b5
Every note of Bbm7b5 is in Bb blues, Bb locrian, Bb altered and Bb half-whole diminished.
Chords near Bbm7b5
Change one note of Bbm7b5 and you have Bbdim (drop the flat seventh), Bbdim7 (the flat seventh becomes a sixth), Bbm7 (the flat fifth becomes a fifth), BbmMaj7b5 (the flat seventh becomes a major seventh) or Bb7b5 (the minor third becomes a major third).
Bbm7b5 is a diminished chord — root, minor third, flat fifth. Diminished and half-diminished chords on every root.
On Bbm7b5’s sound and use this page follows Mark Levine, The Jazz Theory Book (Sher Music, 1995). The shapes and the derived voicings come from different places, and both are explained in where the chords and the theory come from.