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B diminished 7th chord on guitar (Bdim7)
Also called or written Bdim7 or B°7
B diminished 7th contains B, D, F and A♭. The open shape is a compact four-finger grip with two open strings.
How it is built
Formula 1, ♭3, ♭5, ♭♭7
- Root positionB–D–F–A♭Bdim7×-2-0-1-0-1
- First inversionD–F–A♭–BBdim7/D×-×-0-1-0-1
- Second inversionF–A♭–B–DBdim7/F1-2-0-1-0-1
- Third inversionA♭–B–D–FBdim7/A♭4-5-3-4-3-×
How do you play a B diminished 7th chord on guitar?
B diminished 7th is played in open position as × 2 0 1 0 1: ring finger on the A string at fret 2, index finger on the G string at fret 1 and middle finger on the high e string at fret 1. The D and B strings ring open. The low E string stays muted.
Full note and interval breakdown
| String | Fret | Finger | Note |
|---|---|---|---|
| 6 (E) | muted | — | — |
| 5 (A) | 2 | 3 | B (1) |
| 4 (D) | open | — | D (♭3) |
| 3 (G) | 1 | 1 | A♭ (6) |
| 2 (B) | open | — | B (1) |
| 1 (e) | 1 | 2 | F (♭5) |
AdvancedThe open shape requires arching the index finger over the open B string while fretting the G string at the 1st fret.
Open · ×-2-0-1-3-1
B diminished 7th is played in open position as × 2 0 1 3 1: ring finger on the A string at fret 2, index finger on the G string at fret 1, pinky finger on the B string at fret 3 and middle finger on the high e string at fret 1. The D string rings open. The low E string stays muted.
Full note and interval breakdown
| String | Fret | Finger | Note |
|---|---|---|---|
| 6 (E) | muted | — | — |
| 5 (A) | 2 | 3 | B (1) |
| 4 (D) | open | — | D (♭3) |
| 3 (G) | 1 | 1 | A♭ (6) |
| 2 (B) | 3 | 4 | D (♭3) |
| 1 (e) | 1 | 2 | F (♭5) |
1st fret
B diminished 7th is played at the 1st fret as × 2 3 1 3 1: barre your index finger across fret 1, middle finger on the A string at fret 2, ring finger on the D string at fret 3 and pinky finger on the B string at fret 3. The low E string stays muted.
Full note and interval breakdown
| String | Fret | Finger | Note |
|---|---|---|---|
| 6 (E) | muted | — | — |
| 5 (A) | 2 | 2 | B (1) |
| 4 (D) | 3 | 3 | F (♭5) |
| 3 (G) | 1 | 1 (barre) | A♭ (6) |
| 2 (B) | 3 | 4 | D (♭3) |
| 1 (e) | 1 | 1 (barre) | F (♭5) |
6th fret
B diminished 7th is played at the 6th fret as 7 8 6 7 6 ×: barre your index finger across fret 6, middle finger on the low E string at fret 7, pinky finger on the A string at fret 8 and ring finger on the G string at fret 7. The high e string stays muted.
Full note and interval breakdown
| String | Fret | Finger | Note |
|---|---|---|---|
| 6 (E) | 7 | 2 | B (1) |
| 5 (A) | 8 | 4 | F (♭5) |
| 4 (D) | 6 | 1 (barre) | A♭ (6) |
| 3 (G) | 7 | 3 | D (♭3) |
| 2 (B) | 6 | 1 (barre) | F (♭5) |
| 1 (e) | muted | — | — |
7th fret
B diminished 7th is played at the 7th fret as 7 8 9 7 9 7: barre your index finger across fret 7, middle finger on the A string at fret 8, ring finger on the D string at fret 9 and pinky finger on the B string at fret 9.
Full note and interval breakdown
| String | Fret | Finger | Note |
|---|---|---|---|
| 6 (E) | 7 | 1 (barre) | B (1) |
| 5 (A) | 8 | 2 | F (♭5) |
| 4 (D) | 9 | 3 | B (1) |
| 3 (G) | 7 | 1 (barre) | D (♭3) |
| 2 (B) | 9 | 4 | A♭ (6) |
| 1 (e) | 7 | 1 (barre) | B (1) |
Why it sounds like that
B diminished 7th is built from the intervals 1, ♭3, ♭5 and ♭♭7. The ♭♭7, a diminished seventh above the root, gives the chord its tense, symmetrical quality. Compare it with B minor 7th flat 5th, which has a minor seventh instead.
What goes wrong with B diminished 7th?
- Letting the low E string ring instead of muting it.
- Flattening the index finger onto the B string and muting the open note.
- Arching the middle finger too low so it touches the B string.
When to use it
B diminished 7th often resolves to C♯ minor or C♯ major. It suits tense jazz and classical passages.
Changing to and from B diminished 7th
- Sliding the shape up one fret to the 2nd fret gives C diminished 7th.
- From C♯ minor, move the ring finger from the 4th fret of the A string to the 2nd fret and add the index finger on the 1st fret of the G string.
Which voicing to use
The open position keeps the root B in the bass and is the easiest voicing. The 6th fret barre shape moves the root to the low E string for a darker sound.
Other B chords
Common questions
How is B diminished 7th written?
B diminished 7th is written B°7 or Bdim7.
What is the difference between B diminished 7th and B minor 7th flat 5th?
B diminished 7th has a diminished seventh (A♭), while B minor 7th flat 5th has a minor seventh (A). The diminished seventh makes the chord fully diminished and more tense.
Why is the low E string muted in the open shape?
The open low E is not a chord tone of B diminished 7th. Muting it keeps the voicing clean and the bass note on B.