A '''key signature''' in Western musical notation is a graphic representation at the beginning of each staff indicating how many [[sharp (music)|sharp]]s or [[flat (music)|flat]]s are in the piece's main [[key (music)|key]]. The use of a key signature automatically makes the affected notes sharp or flat for the entire piece, unless cancelled out by a natural sign. While it's theoretically possible for any combination of flats and sharps to constitute the key signature, it is usually the case for the key signature to consist either of sharps or flats, but not both. Also unusual are key signatures containing more than six sharps or flats, though one sometimes sees seven in a few extreme cases (more being theoretically impossible). [[Johann Sebastian Bach]] uses seven sharps in the third prelude and fugue of ''Well-Tempered Clavier,'' and [[Beethoven]] uses seven flats in the third movement of his piano sonata Op. 26. | A '''key signature''' in Western musical notation is a graphic representation at the beginning of each staff indicating how many [[sharp (music)|sharp]]s or [[flat (music)|flat]]s are in the piece's main [[key (music)|key]]. The use of a key signature automatically makes the affected notes sharp or flat for the entire piece, unless cancelled out by a natural sign. While it's theoretically possible for any combination of flats and sharps to constitute the key signature, it is usually the case for the key signature to consist either of sharps or flats, but not both. Also unusual are key signatures containing more than six sharps or flats, though one sometimes sees seven in a few extreme cases (more being theoretically impossible). [[Johann Sebastian Bach]] uses seven sharps in the third prelude and fugue of ''Well-Tempered Clavier,'' and [[Beethoven]] uses seven flats in the third movement of his piano sonata Op. 26. |