Double sharp
The double sharp raises a note by two semitones, so by a whole tone. F becomes F double sharp, which sounds like G on the piano. It occurs mainly in extreme keys and in chromatic voice leading, where the spelling is meant to make the voice leading clear.
- Effect
- raises by 2 semitones (a whole tone)
- Name
- “double sharp” added (C double sharp, F double sharp …)
- Example
- F double sharp sounds like G
- Typical in
- extreme keys such as G♯ minor, chromatic lines
- Counterpart
- double flat
Two semitones in one sign
On the page Notation symbols it says: the double sharp raises the note by a whole tone. C becomes C double sharp, which sounds like D, F becomes F double sharp, which sounds like G. The page Name the Note places it in the tone system: there are seven natural notes, and each of them can be raised by a semitone with a sharp, and even by two with a double sharp. From seven letters all the notes needed in notation arise.
| Natural note | With double sharp | Sounds like |
|---|---|---|
| C | C double sharp | D |
| D | D double sharp | E |
| E | E double sharp | F♯ |
| F | F double sharp | G |
| G | G double sharp | A |
| A | A double sharp | B |
| B | B double sharp | C♯ |
Double sharps appear, according to Notation symbols, mainly in extreme keys or in chromatic voice leading. An example is G♯ minor: in harmonic minor the raised seventh degree there is called F double sharp. They are rarer than the single sharp and in practice are often avoided by enharmonic equivalence: instead of C double sharp you write D.
Why not simply G?
The enharmonics exercise gives the reason: the name of a note depends on its function, not on its pitch. A scale uses each letter exactly once. In the theoretical key G♯ major the seventh degree is called F double sharp: if you wrote G, the letter G would occur twice and F not at all.
The exercise page warns against evasion: the second mistake is dodging double accidentals. The equivalent of F♯ is G♭, but the equivalent of F double sharp is G. Such cases seem contrived, but follow inevitably from the system and occur in real literature.
Double sharp and key signature
A double sharp is almost always written as an accidental within the bar, not in the key signature. The key signature, according to Notation symbols, contains up to seven sharps or seven flats in a standardised order, double signs do not belong to it. More on the relationship of the signs: see Accidental and Sharp.
Common mistakes
- Confusing the double sharp with two sharps: The double sharp is a single sign for two semitones. Two single sharps in a row do not exist.
- Confusing F double sharp and G♯: F double sharp sounds like G, not like G♯.
- “Calculating away” the double sharp: If you always switch to the enharmonic spelling at once, you lose the voice leading. The leading tone of G♯ major is called F double sharp, not G.
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Related terms
SharpDouble flatNatural signAccidental (in the bar)Enharmonic equivalenceG♯ majorF♯ majorC♯ majorAccidental
Editor: Maik Krohm · reviewed on 3 October 2026
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