Double flats and sharps Key signatures can theoretically be extended through double flats or double sharps and beyond, but this is extremely rare. For example, the key of G major would have eight sharps, requiring six single sharps and an F double-sharp (F). The key of A major, with four flats, is enharmonically equivalent and would generally be used instead. MajorKey signatureMinorF major (E major)8 flats (4 sharps)D minor (C minor)B major (A major)9 flats (3 sharps)G minor (F minor)E major (D major)10 flats (2 sharps)C minor (B minor)A major (G major)11 flats (1 sharp)F minor (E minor)D major (C major)12 flats (no flats or sharps)B minor (A minor)G major (F major)13 flats (1 flat)E minor (D minor)C major (B major)14 flats (2 flats)A minor (G minor)G major (A major)8 sharps (4 flats)E minor (F minor)D major (E major)9 sharps (3 flats)B minor (C minor)A major (B major)10 sharps (2 flats)F minor (G minor)E major (F major)11 sharps (1 flat)C minor (D minor)B major (C major)12 sharps (no flats or sharps)G minor (A minor)F major (G major)13 sharps (1 sharp)D minor (E minor)C major (D major)14 sharps (2 sharps)A minor (B minor) A piece in a major key might modulate up a fifth to the dominant (a common occurrence in Western music), resulting in a new key signature with an additional sharp. If the original key was C-sharp, such a modulation would lead to the theoretical key of G-sharp major (with eight sharps) requiring an F in place of the F. This section could be written using the enharmonically equivalent key signature of A-flat major instead. Claude Debussy's Suite bergamasque does this: in the third movement "Clair de lune" the key shifts from D-flat major to D-flat minor (eight flats) for a few measures but the passage is notated in C-sharp minor (four sharps); the same happens in the final movement, "Passepied", in which a G-sharp major section is written as A-flat major.
Double flats and sharps Key signatures can theoretically be extended through double flats or double sharps and beyond, but this is extremely rare. For example, the key of G major would have eight sharps, requiring six single sharps and an F double-sharp (F). The key of A major, with four flats, is enharmonically equivalent and would generally be used instead. MajorKey signatureMinorF major (E major)8 flats (4 sharps)D minor (C minor)B major (A major)9 flats (3 sharps)G minor (F minor)E major (D major)10 flats (2 sharps)C minor (B minor)A major (G major)11 flats (1 sharp)F minor (E minor)D major (C major)12 flats (no flats or sharps)B minor (A minor)G major (F major)13 flats (1 flat)E minor (D minor)C major (B major)14 flats (2 flats)A minor (G minor)G major (A major)8 sharps (4 flats)E minor (F minor)D major (E major)9 sharps (3 flats)B minor (C minor)A major (B major)10 sharps (2 flats)F minor (G minor)E major (F major)11 sharps (1 flat)C minor (D minor)B major (C major)12 s?harps (no flats or sharps)G minor (A minor)F major (G major)13 sharps (1 sharp)D minor (E minor)C major (D major)14 sharps (2 sharps)A minor (B minor) A piece in a major key might modulate up a fifth to the dominant (a common occurrence in Western music), resulting in a new key signature with an additional sharp. If the original key was C-sharp, such a modulation would lead to the theoretical key of G-sharp major (with eight sharps) requiring an F in place of the F. This section could be wr!itten using the enharmonically equivalent key signature of A-flat major instead. Claude Debussy's Suite bergamasque does this: in the thi.rd movement "Clair de lune" the key shifts from D-flat major to D-flat minor (eight flats) for a few measures but the passage is notated in C-sharp minor (four sharps); the same happens in the final movement, "Passepied", in which a G-sharp major section is written as A-flat major.