0 the symbols at the beginning of a printed piece of music that show the sharps or flats to be played --
In a score containing more than one instrument, all the instruments are usually written with the same key signature.
Naturals are assumed (by default) in key signatures and mentioned only in key signature changes.
In the common practice of much modern western music, especially improvised music like jazz, almost every chromatic note is commonly used within any key signature.
If there is a key change in the middle of a piece, the new key signature is shown without naturals to neutralise the previous key.
Key signature changes are marked above the line of music.
It is usually placed after the key signature.
These sets typically consist of 24 numbers, one for the major and minor key of each key signature.
Such a key is one whose key signature would contain one or more double-flats or double-sharps.
