Scale degrees · F major
The ♭13 of F is D♭
The ♭13 (flat thirteen, written b13) of F is D♭ (D flat): a minor thirteenth above the root.
F — the root, 1D♭ — the ♭13
How to find it
A 13th is a 6th an octave up, so it takes the 6th's letter: F, G, A, B, C, D.
Then the sound: a minor thirteenth is 20 semitones above F, and the D that is 20 semitones up is D♭.
That is why it is D♭ and not C♯: C♯ is the same key on the piano, but from F it would be a 12th, not a 13th.
Where you meet it
The ♭13 is an altered tension of the dominant chord, one of the notes of the altered scale.
In F7♭13:
F · A · C · E♭ · D♭
The ♭13 in every key
| Key | The ♭13 |
|---|---|
| C | A♭ |
| G | E♭ |
| D | B♭ |
| A | F |
| E | C |
| B | G |
| F♯ | D |
| D♭ | B𝄫 |
| A♭ | F♭ |
| E♭ | C♭ |
| B♭ | G♭ |
| F | D♭ |
Every degree of F
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