The ♭3 of A♭ is C♭
The ♭3 (flat three, written b3) of A♭ (A flat, Ab) is C♭ (C flat): a minor third above the root.
How to find it
Count letters first, the root included: A, B, C. A 3rd lands on C.
Then the sound: a minor third is 3 semitones above A♭, and the C that is 3 semitones up is C♭.
That is why it is C♭ and not B: B is the same key on the piano, but from A♭ it would be a 2nd, not a 3rd.
Where you meet it
The ♭3 makes a chord minor: A♭ minor is the root, C♭ and the 5th. Over a dominant chord the same key on the piano is usually written as the ♯9, with another letter.
In A♭ minor:
A♭ · C♭ · E♭
The ♭3 in every key
| Key | The ♭3 |
|---|---|
| C | E♭ |
| G | B♭ |
| D | F |
| A | C |
| E | G |
| B | D |
| F♯ | A |
| D♭ | F♭ |
| A♭ | C♭ |
| E♭ | G♭ |
| B♭ | D♭ |
| F | A♭ |
Every degree of A♭
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