Scale degrees · A♭ major
The ♭13 of A♭ is F♭
The ♭13 (flat thirteen, written b13) of A♭ (A flat, Ab) is F♭ (F flat): a minor thirteenth above the root.
A♭ — the root, 1F♭ — the ♭13
How to find it
A 13th is a 6th an octave up, so it takes the 6th's letter: A, B, C, D, E, F.
Then the sound: a minor thirteenth is 20 semitones above A♭, and the F that is 20 semitones up is F♭.
That is why it is F♭ and not E: E is the same key on the piano, but from A♭ 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 A♭7♭13:
A♭ · C · E♭ · G♭ · F♭
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 A♭
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