The sharps or flats that follow the clef and indicate the key; SYN. signature.
In music, sharps or flats indicating a prevailing key; the symbols for these are inserted on the score at the beginning of a musical stave, after the clef. A key signature without sharps or flats signifies C major or A minor, or that the music is atonal.
A change of key signature during a piece is indicated by a double bar at which any cancellation of elements of the previous key signature is shown by natural signs prior to or incorporated in the new key signature.