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 the signature. In the major key with four flats (B E A D), for example, the penultimate flat is A, indicating a key of A major. In this case each new scale starts a fifth "below" (or a fourth above) the previous one. A key signature is not the same as a key; key signatures are merely notational devices. They are convenient principally for diatonic or tonal music. The key signature defines the diatonic scale that a piece of music uses without the need for accidentals. Most scales require that some notes be consistently sharped or flatted. For example, the