Scale degrees · C major
The ♯4 of C is F♯
The ♯4 (sharp four, written #4) of C is F♯ (F sharp): an augmented fourth above the root.
C — the root, 1F♯ — the ♯4
How to find it
Count letters first, the root included: C, D, E, F. A 4th lands on F.
Then the sound: an augmented fourth is 6 semitones above C, and the F that is 6 semitones up is F♯.
That is why it is F♯ and not G♭: G♭ is the same key on the piano, but from C it would be a 5th, not a 4th.
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 C Lydian:
C · D · E · F♯ · G · A · B
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 C
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