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B♭ minor 7th flat 5th chord on bass (B♭m7♭5)
Also called or written B♭m7♭5, B♭ or B♭ Half Diminished Minor 7
B♭ minor 7th flat 5th contains B♭, D♭, F♭ and A♭. The 6th-fret shape requires a wide stretch between the index and pinky fingers.
How it is built
Formula 1, ♭3, ♭5, ♭7
- Root positionB♭–D♭–F♭–A♭B♭m7♭56-7-6-6
- First inversionD♭–F♭–A♭–B♭B♭m7♭5/D♭no shape on this instrument
- Second inversionF♭–A♭–B♭–D♭B♭m7♭5/F♭12-13-11-13
- Third inversionA♭–B♭–D♭–F♭B♭m7♭5/A♭4-4-2-3
How do you play a B♭ minor 7th flat 5th chord on bass?
B♭ minor 7th flat 5th is played at the 6th fret as 6 7 6 6: index finger on the E string at fret 6, pinky finger on the A string at fret 7, middle finger on the D string at fret 6 and ring finger on the G string at fret 6.
Full note and interval breakdown
| String | Fret | Finger | Note |
|---|---|---|---|
| 4 (E) | 6 | 1 | B♭ (1) |
| 3 (A) | 7 | 4 | F♭ (♭5) |
| 2 (D) | 6 | 2 | A♭ (♭7) |
| 1 (G) | 6 | 3 | D♭ (♭3) |
AdvancedThe wide stretch between the index finger on the 4th string and the pinky on the 3rd string at the 6th fret is the hardest part.
B♭m7♭5/F♭ inversion
B♭ minor 7th flat 5th is played at the 11th fret as 12 13 11 13: middle finger on the E string at fret 12, ring finger on the A string at fret 13, index finger on the D string at fret 11 and pinky finger on the G string at fret 13.
Full note and interval breakdown
| String | Fret | Finger | Note |
|---|---|---|---|
| 4 (E) | 12 | 2 | F♭ (♭5) |
| 3 (A) | 13 | 3 | B♭ (1) |
| 2 (D) | 11 | 1 | D♭ (♭3) |
| 1 (G) | 13 | 4 | A♭ (♭7) |
B♭m7♭5/A♭ inversion
B♭ minor 7th flat 5th is played at the 2nd fret as 4 4 2 3: ring finger on the E string at fret 4, pinky finger on the A string at fret 4, index finger on the D string at fret 2 and middle finger on the G string at fret 3.
Full note and interval breakdown
| String | Fret | Finger | Note |
|---|---|---|---|
| 4 (E) | 4 | 3 | A♭ (♭7) |
| 3 (A) | 4 | 4 | D♭ (♭3) |
| 2 (D) | 2 | 1 | F♭ (♭5) |
| 1 (G) | 3 | 2 | B♭ (1) |
Why it sounds like that
B♭ minor 7th flat 5th is built from the formula 1, ♭3, ♭5, ♭7. The diminished 5th between B♭ and F♭ creates the chord's characteristic tension. Raising the ♭5 to a perfect 5th produces B♭ minor 7th, the closest stable contrast.
What goes wrong with B♭ minor 7th flat 5th?
- Letting the pinky collapse and mute the 2nd string.
- Fretting the 1st string with the ring finger too far from the fret, causing a buzz.
- Allowing the index finger to touch the 3rd string and deaden the B♭.
When to use it
B♭ minor 7th flat 5th functions as the ii chord in A♭ natural minor and the vii chord in B major. Use it in minor-key jazz and blues lines where the half-diminished colour leads to a dominant. It pairs naturally with B♭ minor and B♭ 5th.
Changing to and from B♭ minor 7th flat 5th
- Sliding the shape down one fret to the 5th fret gives A minor 7th flat 5th.
- Sliding the shape up one fret to the 7th fret gives B minor 7th flat 5th.
Which voicing to use
The 6th-fret root position keeps B♭ in the bass for a grounded sound. The B♭m7♭5/E inversion at the 12th fret places the diminished 5th in the bass, creating a darker, less stable feel. Choose the B♭m7♭5/G♯ inversion when the bass line needs to descend to A♭.
Other B♭ chords
Common questions
How is B♭ minor 7th flat 5th written?
B♭ minor 7th flat 5th is written as B♭m7♭5, and it is also called Half Diminished Minor 7. The ASCII root spelling is Bb. It is also spelled A♯ in enharmonic notation for the same sounding root.
What is the difference between B♭ minor 7th flat 5th and B♭ diminished?
B♭ minor 7th flat 5th adds a minor 7th to the diminished triad. B♭ diminished has only the root, ♭3 and ♭5.
Why does B♭ minor 7th flat 5th sound unstable?
The tritone between B♭ and F♭ creates tension that wants to resolve. This instability makes the chord useful as a passing harmony.