What Bdim7 is built from
Counting up in semitones from B:
| Note | Interval | Semitones from root |
|---|---|---|
| B | root | 0 |
| D | minor third | 3 |
| F | diminished fifth | 6 |
| A♭ | diminished seventh | 9 |
Move all four of those the same distance and you get the same chord on another root — that is what the diminished seventh formula 0 – 3 – 6 – 9 means.
How to play Bdim7
Leave the low E string out. Nothing is higher than fret 4, so it sits in first position.
All four strings are played. Nothing is higher than fret 2, so it sits in first position.
Play B, D, F and A♭ together. That is three white keys and one black.
Numbers in the grids are frets. Where a number is printed beside a grid, that is the fret the top row stands for; otherwise the thick bar at the top is the nut. A circle above a string means play it open, a cross means leave it out.
Guitar, string by string
| Guitar string | Stopped at | Sounds |
|---|---|---|
| low E | not played | — |
| A | fret 2 | B |
| D | fret 3 | F |
| G | fret 4 | B |
| B | fret 3 | D |
| top E | fret 4 | A♭ |
Ukulele, string by string
| Ukulele string | Stopped at | Sounds |
|---|---|---|
| G | fret 1 | A♭ |
| C | fret 2 | D |
| E | fret 1 | F |
| A | fret 2 | B |
Bdim7 on the stave
The same four notes written on a treble stave, spelled the way a diminished seventh is spelled — one letter for every other step, with whichever accidental reaches the pitch. That is why it reads B, D, F and A♭, and not the same sounds written some other way.
Which keys Bdim7 belongs to
No major scale contains all four of these notes. It does sit inside the harmonic minor scale, which is where it is usually met:
- C harmonic minor, on degree vii°7
Other chords on B
Same root, different notes above it.
Chords straight off a recording
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