Scale degrees · F major
The ♭9 of F is G♭
The ♭9 (flat nine, written b9) of F is G♭ (G flat): a minor ninth above the root.
F — the root, 1G♭ — the ♭9
How to find it
A 9th is a 2nd an octave up, so it takes the 2nd's letter: F, G.
Then the sound: a minor ninth is 13 semitones above F, and the G that is 13 semitones up is G♭.
That is why it is G♭ and not F♯: F♯ is the same key on the piano, but from F 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 F7♭9:
F · A · C · E♭ · G♭
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 F
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