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B♭ diminished 7th chord on guitar (B♭dim7)
Also called or written B♭dim7 or B♭°7
B♭ diminished 7th is built from B♭, D♭, F♭, and A♭♭. The open voicing keeps the bass on the A string while two open strings ring through.
How it is built
Formula 1, ♭3, ♭5, ♭♭7
- Root positionB♭–D♭–F♭–A♭♭B♭dim7×-1-2-0-2-0
- First inversionD♭–F♭–A♭♭–B♭B♭dim7/D♭×-4-2-3-2-3
- Second inversionF♭–A♭♭–B♭–D♭B♭dim7/F♭0-1-2-0-2-0
- Third inversionA♭♭–B♭–D♭–F♭B♭dim7/A♭♭3-1-2-0-2-0
How do you play a B♭ diminished 7th chord on guitar?
B♭ diminished 7th is played in open position as × 1 2 0 2 0: index finger on the A string at fret 1, middle finger on the D string at fret 2 and ring finger on the B string at fret 2. The G and high e strings ring open. The low E string stays muted.
Full note and interval breakdown
| String | Fret | Finger | Note |
|---|---|---|---|
| 6 (E) | muted | — | — |
| 5 (A) | 1 | 1 | B♭ (1) |
| 4 (D) | 2 | 2 | F♭ (♭5) |
| 3 (G) | open | — | A♭♭ (6) |
| 2 (B) | 2 | 3 | D♭ (♭3) |
| 1 (e) | open | — | F♭ (♭5) |
AdvancedThe open voicing demands precise muting of the low E string while fretting three strings cleanly.
Open · A♭♭ on top
B♭ diminished 7th is played in open position as × 1 2 0 2 3: index finger on the A string at fret 1, middle finger on the D string at fret 2, ring finger on the B string at fret 2 and pinky finger on the high e string at fret 3. The G string rings open. The low E string stays muted.
Full note and interval breakdown
| String | Fret | Finger | Note |
|---|---|---|---|
| 6 (E) | muted | — | — |
| 5 (A) | 1 | 1 | B♭ (1) |
| 4 (D) | 2 | 2 | F♭ (♭5) |
| 3 (G) | open | — | A♭♭ (6) |
| 2 (B) | 2 | 3 | D♭ (♭3) |
| 1 (e) | 3 | 4 | A♭♭ (6) |
5th fret
B♭ diminished 7th is played at the 5th fret as 6 7 5 6 5 ×: barre your index finger across fret 5, middle finger on the low E string at fret 6, pinky finger on the A string at fret 7 and ring finger on the G string at fret 6. The high e string stays muted.
Full note and interval breakdown
| String | Fret | Finger | Note |
|---|---|---|---|
| 6 (E) | 6 | 2 | B♭ (1) |
| 5 (A) | 7 | 4 | F♭ (♭5) |
| 4 (D) | 5 | 1 (barre) | A♭♭ (6) |
| 3 (G) | 6 | 3 | D♭ (♭3) |
| 2 (B) | 5 | 1 (barre) | F♭ (♭5) |
| 1 (e) | muted | — | — |
6th fret
B♭ diminished 7th is played at the 6th fret as 6 7 8 6 8 6: barre your index finger across fret 6, middle finger on the A string at fret 7, ring finger on the D string at fret 8 and pinky finger on the B string at fret 8.
Full note and interval breakdown
| String | Fret | Finger | Note |
|---|---|---|---|
| 6 (E) | 6 | 1 (barre) | B♭ (1) |
| 5 (A) | 7 | 2 | F♭ (♭5) |
| 4 (D) | 8 | 3 | B♭ (1) |
| 3 (G) | 6 | 1 (barre) | D♭ (♭3) |
| 2 (B) | 8 | 4 | A♭♭ (6) |
| 1 (e) | 6 | 1 (barre) | B♭ (1) |
8th fret
B♭ diminished 7th is played at the 8th fret as × × 8 9 8 9: index finger on the D string at fret 8, ring finger on the G string at fret 9, middle finger on the B string at fret 8 and pinky finger on the high e string at fret 9. The low E and A strings stay muted.
Full note and interval breakdown
| String | Fret | Finger | Note |
|---|---|---|---|
| 6 (E) | muted | — | — |
| 5 (A) | muted | — | — |
| 4 (D) | 8 | 1 | B♭ (1) |
| 3 (G) | 9 | 3 | F♭ (♭5) |
| 2 (B) | 8 | 2 | A♭♭ (6) |
| 1 (e) | 9 | 4 | D♭ (♭3) |
Why it sounds like that
B♭ diminished 7th stacks three minor 3rds on B♭: 1, ♭3, ♭5, ♭♭7. The diminished 5th between B♭ and F♭ gives the chord its tense, unstable quality. Compare it with B♭ minor 7th flat 5th, which raises the ♭♭7 to a ♭7.
What goes wrong with B♭ diminished 7th?
- Letting the low E string ring out, which changes the bass note from B♭ to E.
- Flattening the middle finger onto the G string, killing the open note.
- Pressing the ring finger too hard on the B string, causing the high E to buzz.
When to use it
B♭ diminished 7th often substitutes for the ♭III in G minor, resolving to C minor or C major. Its unstable sound suits passing chords in classical and jazz, or as a dramatic transition in rock. Try it before C minor or C major.
Changing to and from B♭ diminished 7th
- Move to <a href="/guitar/a-flat-dim-7-chord">A♭ diminished 7th</a> by sliding the shape down two frets to the 3rd fret.
- Shift to <a href="/guitar/b-dim-7-chord">B diminished 7th</a> by moving the fretted notes up one fret while keeping the open strings.
Which voicing to use
The open voicing keeps B♭ in the bass and is easiest for quick changes. The 5th fret barre version offers a darker, more sustained sound with the same bass note but higher register.
Other B♭ chords
Common questions
How is B♭ diminished 7th written?
B♭ diminished 7th is written B♭°7 or B♭dim7. On a keyboard, use Bb for the root. It is also spelled A♯ in enharmonic notation for the same sounding root.
What is the difference between B♭ diminished 7th and B♭ minor 7th flat 5th?
B♭ diminished 7th has a ♭♭7 (A♭♭), while B♭ minor 7th flat 5th has a ♭7 (A♭). The diminished 7th chord is more dissonant and symmetrical.
Why does B♭ diminished 7th sound unstable?
B♭ diminished 7th contains two diminished 5th intervals, creating strong tension. The chord wants to resolve, usually to a chord a half step above one of its notes.