The 𝄫7 of C is B𝄫
The 𝄫7 (double-flat seven, written bb7) of C is B𝄫 (B double flat): a diminished seventh above the root.
How to find it
Count letters first, the root included: C, D, E, F, G, A, B. A 7th lands on B.
Then the sound: a diminished seventh is 9 semitones above C, and the B that is 9 semitones up is B𝄫.
That is why it is B𝄫 and not A: A is the same key on the piano, but from C it would be a 6th, not a 7th.
Where you meet it
The 𝄫7 is the 7th of the fully diminished chord. On the piano it is the same key as the 6, but a seventh is spelled with a seventh's letter.
In C°7:
C · E♭ · G♭ · B𝄫
The 𝄫7 in every key
| Key | The 𝄫7 |
|---|---|
| C | B𝄫 |
| G | F♭ |
| D | C♭ |
| A | G♭ |
| E | D♭ |
| B | A♭ |
| F♯ | E♭ |
| D♭ | C𝄫 |
| A♭ | G𝄫 |
| E♭ | D𝄫 |
| B♭ | A𝄫 |
| F | E𝄫 |
Every degree of C
Free on iPhone and Android
Name it before
you can count it.
Improvy trains every degree in all 12 keys — the 3, the ♭7, the ♯11 — until you see the note without working it out. A few minutes a day. Free to start; Pro is one payment, never a subscription.
Or try the 60-second test in your browser