Scale degrees · A♭ major
The 9 of A♭ is B♭
The 9 (nine) of A♭ (A flat, Ab) is B♭ (B flat): a major ninth above the root.
A♭ — the root, 1B♭ — the 9
How to find it
A 9th is a 2nd an octave up, so it takes the 2nd's letter: A, B.
Then the sound: a major ninth is 14 semitones above A♭, and the B that is 14 semitones up is B♭.
That is why it is B♭ and not A♯: A♯ is the same key on the piano, but from A♭ it would be an 8th, not a 9th.
Where you meet it
The 9 is the 2 an octave up: the first extension on almost any chord, major, minor or dominant.
In A♭maj9:
A♭ · C · E♭ · G · B♭
The 9 in every key
| Key | The 9 |
|---|---|
| C | D |
| G | A |
| D | E |
| A | B |
| E | F♯ |
| B | C♯ |
| F♯ | G♯ |
| D♭ | E♭ |
| A♭ | B♭ |
| E♭ | F |
| B♭ | C |
| F | G |
Every degree of A♭
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