Scale degrees · A major
The ♭9 of A is B♭
The ♭9 (flat nine, written b9) of A is B♭ (B flat): a minor 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 minor ninth is 13 semitones above A, and the B that is 13 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 first altered tension on a dominant chord. It is the ♭2 an octave up, written as a 9 because it sits above the chord.
In A7♭9:
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
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