Key signature key signatures showing sharps or flats on both octaves for notes which fall within the staff. An accidental is an exception to the key signature, applying only to the measure and octave in which it appears. Although a key signature may be written using any combination of sharp and flat symbols, the most common series of thirteen homogeneous key signatures—ranging from six flats to six sharps, with each successive flat or sharp placed on the note a perfect fifth below or above, respectively, the previous one—is assumed in much of this article. A piece scored using a single diatonic key
Key signature of sharps or flats (which is the same in any clef), rather than their position on the staff. For example, if a key signature has only one sharp, it must be an F-sharp, which corresponds to a G major or an E minor key. However, in 20th-century music, there are occasional exceptions to this, where a piece uses an unorthodox or synthetic scale, where a key signature may be invented to reflect this. This may consist of a number of sharps or flats that are not the normal ones (such as a signature of just C or E), or it