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B diminished chord on bass (Bdim)
Also called or written Bdim or B°
B diminished contains B, D, and F. The 7th-fret shape is a one-finger-per-string stretch that sits in the middle of the neck.
How it is built
Formula 1, ♭3, ♭5
How do you play a B diminished chord on bass?
B diminished is played at the 7th fret as 7 8 9 7: index finger on the E string at fret 7, ring finger on the A string at fret 8, pinky finger on the D string at fret 9 and middle finger on the G string at fret 7.
Full note and interval breakdown
| String | Fret | Finger | Note |
|---|---|---|---|
| 4 (E) | 7 | 1 | B (1) |
| 3 (A) | 8 | 3 | F (♭5) |
| 2 (D) | 9 | 4 | B (1) |
| 1 (G) | 7 | 2 | D (♭3) |
IntermediateThe pinky must reach the 9th fret on the 2nd string while the middle finger holds the 7th fret on the 1st string.
Bdim/D inversion
B diminished is played at the 8th fret as 10 8 9 10: ring finger on the E string at fret 10, index finger on the A string at fret 8, middle finger on the D string at fret 9 and pinky finger on the G string at fret 10.
Full note and interval breakdown
| String | Fret | Finger | Note |
|---|---|---|---|
| 4 (E) | 10 | 3 | D (♭3) |
| 3 (A) | 8 | 1 | F (♭5) |
| 2 (D) | 9 | 2 | B (1) |
| 1 (G) | 10 | 4 | F (♭5) |
Bdim/F inversion · open position
B diminished is played in open position as 1 2 0 ×: index finger on the E string at fret 1 and middle finger on the A string at fret 2. The D string rings open. The G string stays muted.
Full note and interval breakdown
| String | Fret | Finger | Note |
|---|---|---|---|
| 4 (E) | 1 | 1 | F (♭5) |
| 3 (A) | 2 | 2 | B (1) |
| 2 (D) | open | — | D (♭3) |
| 1 (G) | muted | — | — |
Bdim/F inversion · fret 7
B diminished is played at the 7th fret as × 8 9 7: middle finger on the A string at fret 8, ring finger on the D string at fret 9 and index finger on the G string at fret 7. The E string stays muted.
Full note and interval breakdown
| String | Fret | Finger | Note |
|---|---|---|---|
| 4 (E) | muted | — | — |
| 3 (A) | 8 | 2 | F (♭5) |
| 2 (D) | 9 | 3 | B (1) |
| 1 (G) | 7 | 1 | D (♭3) |
Bdim/F inversion · fret 12
B diminished is played at the 12th fret as 13 14 12 ×: middle finger on the E string at fret 13, ring finger on the A string at fret 14 and index finger on the D string at fret 12. The G string stays muted.
Full note and interval breakdown
| String | Fret | Finger | Note |
|---|---|---|---|
| 4 (E) | 13 | 2 | F (♭5) |
| 3 (A) | 14 | 3 | B (1) |
| 2 (D) | 12 | 1 | D (♭3) |
| 1 (G) | muted | — | — |
Why it sounds like that
B diminished is built from the formula 1, ♭3, ♭5. The ♭5 interval gives the chord its tense, unstable quality. Compare B minor, which raises the fifth to F♯.
What goes wrong with B diminished?
- Letting the pinky collapse onto the 1st string mutes the G.
- Pressing the index finger too flat on the 4th string buzzes against the fret.
- Arching the ring finger too high pulls the 3rd string sharp.
When to use it
B diminished works as a passing chord between B minor and D major, or over an A natural minor line. The ♭5 interval creates a tritone that pulls toward the next chord, suiting jazz walk-ups and metal riffs.
Changing to and from B diminished
- Sliding the shape down two frets to the 5th fret gives A diminished.
- Move to B minor by raising the 2nd string one fret to the 10th fret.
Which voicing to use
The 7th-fret shape puts B in the bass for a root-position sound. The Bdim/D inversion at the 10th fret places D in the bass, which softens the chord's bite.
Other B chords
Common questions
How do I write B diminished?
Write B° or Bdim. The root is B, and the chord is spelled B–D–F.
Why does B diminished sound unstable?
The ♭5 interval creates a tritone with the root, which wants to resolve. This tension is what gives diminished chords their forward drive.
Can I use B diminished in place of B minor?
Only when you want that darker, more dissonant color. B diminished lowers the fifth, so it clashes with melodies that expect the perfect fifth F♯.