A close-position chord with the second voice from the top lowered an octave. Sits on four adjacent strings.
Bbmaj7b5 is Bb, D, Fb and A — Bbmaj7 with the fifth lowered a semitone.
It sounds hollow and hard to place. Far more often met spelled the other way round, as a ♯11 over a chord that kept its fifth.

| Bb | D | Fb | A |
|---|---|---|---|
| 1 | 3 | ♭5 | 7 |
Coloured tonic — rare, and unstable for a major chord.
Also written BbM7b5, BbΔ7b5 or Bbmaj7(b5). The same chord either way; which spelling you meet depends on who wrote the chart.
Take the four notes stacked as close together as they go, then drop the second voice from the top an octave. The gap it opens is what makes the chord sound like a chord rather than a cluster.
It lands on four adjacent strings, which is why it is the workhorse voicing on guitar.
Bbmaj7b5 has 14 of them, on the bottom four strings, the middle four strings and the top four strings, from open position up to the 13th — every inversion the chord has: Bb in the bass, D in the bass, Fb in the bass and A in the bass. The one to learn first is the Fb shape at the nut, which is the easiest grip here.
5 of them sit on the bottom four strings, 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 x1223x — no barre and down at the nut. None of the shapes for Bbmaj7b5 uses an open string, so every one of them is movable; the lowest sits at the 1st fret. 3 of the 7 need a barre. Together they cover the neck from the 1st fret to the 15th.
| Frets | Where | Bass | Top | Hand |
|---|---|---|---|---|
| x1223x | 1st fret | Bb, root position | D | all fretted |
| 657755 | 5th fret | Bb, root position | A | barred |
| 6777x0 | 6th fret | Bb, root position | Fb | barred |
| 6777x6 | 6th fret | Bb, root position | Bb | barred |
| x-x-8-9-10-10 | 8th fret | Bb, root position | D | all fretted |
| x-13-12-14-15-12 | 12th fret | Bb, root position | Fb | all fretted |
| x-13-14-14-15-x | 13th fret | Bb, root position | D | all fretted |
The same notes rebuilt from scratch give 7 shell, 9 drop 3 and 6 open string voicings, each on its own page.
Tensions. A shell of Bbmaj7b5, root, third and seventh, leaves a string free, and the tones that belong over it are the 9 (C) and the 13 (G).
How you get to it. The turn that lands on Bbmaj7b5 is Cm7 to F7 — the ii and the V of Bb — and F7 shares its third and seventh with Cm7, so the hand barely moves between them.
In which keys. Every note of Bbmaj7b5 belongs to D minor (the ♭VI) and F major (the IV, the subdominant).
Every note of Bbmaj7b5 is in Bb lydian.
Change one note of Bbmaj7b5 and you have Bbmaj7 (the flat fifth becomes a fifth), Bbmaj7#5 (the flat fifth becomes a sharp fifth), BbmMaj7b5 (the major third becomes a minor third) or Bb7b5 (the major seventh becomes a flat seventh).
Bbmaj7b5 is a major chord — root, major third, fifth. Major chords on every root.
On Bbmaj7b5’s sound and use this page follows Robert Rawlins & Nor Eddine Bahha, Jazzology (Hal Leonard, 2005). The shapes and the derived voicings come from different places, and both are explained in where the chords and the theory come from.
Shows each chord the way this style would voice it, and marks which of its alternatives belong to the idiom.