Also written Bdim7 or B°7
B diminished 7th contains B, D, F, and A♭. This advanced ukulele shape demands four fretted notes in a compact two-fret cluster, testing precise finger placement.
The same three notes, with a different one in the bass.
B diminished 7th is built from the formula 1, ♭3, ♭5, ♭♭7. The diminished 5th between B and F creates the chord's tense quality, while the ♭♭7 (A♭) is a major 6th above the root. Compare it to B minor 7th flat 5th, which has a minor seventh instead.
B diminished 7th often functions as a leading-tone chord in C major or C minor, resolving to C♯ major or C♯ minor. Its dissonance suits jazz, classical, and dramatic passages.
The default Bdim7/D inversion places D in the bass, giving a slightly softer edge. The 10th fret position has B in the bass for a root-position sound. Choose based on the bass movement you want.
B diminished 7th is played at the 1st fret as 1 2 1 2: index finger on the G string at fret 1, ring finger on the C string at fret 2, middle finger on the E string at fret 1 and pinky finger on the A string at fret 2.
Tip — The hardest part is fitting four fingers into a two-fret span without muting adjacent strings.
| String | Fret | Finger | Note |
|---|---|---|---|
| 4 (G) | 1 | 1 | A♭ (♭♭7) |
| 3 (C) | 2 | 3 | D (♭3) |
| 2 (E) | 1 | 2 | F (♭5) |
| 1 (A) | 2 | 4 | B (1) |
B diminished 7th is played at the 4th fret as 4 5 4 5: index finger on the G string at fret 4, ring finger on the C string at fret 5, middle finger on the E string at fret 4 and pinky finger on the A string at fret 5.
| String | Fret | Finger | Note |
|---|---|---|---|
| 4 (G) | 4 | 1 | B (1) |
| 3 (C) | 5 | 3 | F (♭5) |
| 2 (E) | 4 | 2 | A♭ (♭♭7) |
| 1 (A) | 5 | 4 | D (♭3) |
B diminished 7th is played at the 7th fret as 7 8 7 8: index finger on the G string at fret 7, ring finger on the C string at fret 8, middle finger on the E string at fret 7 and pinky finger on the A string at fret 8.
| String | Fret | Finger | Note |
|---|---|---|---|
| 4 (G) | 7 | 1 | D (♭3) |
| 3 (C) | 8 | 3 | A♭ (♭♭7) |
| 2 (E) | 7 | 2 | B (1) |
| 1 (A) | 8 | 4 | F (♭5) |
B diminished 7th is played at the 10th fret as 10 11 10 11: index finger on the G string at fret 10, ring finger on the C string at fret 11, middle finger on the E string at fret 10 and pinky finger on the A string at fret 11.
| String | Fret | Finger | Note |
|---|---|---|---|
| 4 (G) | 10 | 1 | F (♭5) |
| 3 (C) | 11 | 3 | B (1) |
| 2 (E) | 10 | 2 | D (♭3) |
| 1 (A) | 11 | 4 | A♭ (♭♭7) |
Bdim7 has a double-flatted seventh (A♭), while Bm7♭5 has a minor seventh (A). The dim7 chord is fully diminished, with all minor third intervals.
Bdim7 contains two tritones: B–F and D–A♭. These dissonant intervals create tension that demands resolution.
Yes, Bdim7 works as a passing chord between diatonic chords, especially in jazz and classical progressions. Its symmetrical structure allows smooth voice leading.