Scale degrees · B♭ major
The ♯4 of B♭ is E
The ♯4 (sharp four, written #4) of B♭ (B flat, Bb) is E: an augmented fourth above the root.
B♭ — the root, 1E — the ♯4
How to find it
Count letters first, the root included: B, C, D, E. A 4th lands on E.
Then the sound: an augmented fourth is 6 semitones above B♭, which is exactly where E is — no sharp or flat needed.
Where you meet it
The ♯4 is the Lydian note, a tritone above the root. On a chord symbol it is usually written ♯11.
In the scale B♭ Lydian:
B♭ · C · D · E · F · G · A
The ♯4 in every key
| Key | The ♯4 |
|---|---|
| C | F♯ |
| G | C♯ |
| D | G♯ |
| A | D♯ |
| E | A♯ |
| B | E♯ |
| F♯ | B♯ |
| D♭ | G |
| A♭ | D |
| E♭ | A |
| B♭ | E |
| F | B |
Every degree of B♭
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