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
Shape note followed (ascending) by Sol, La, etc. The first note of a minor key is always La, followed by Mi, Fa, etc. The first three notes of any major scale – fa, sol, la – are each a tone apart. The fourth to sixth notes are also a tone apart and are also fa, sol, la. The seventh and eighth notes, being separated by a semitone, are indicated mi-fa. This means that just four shapenotes can adequately reflect the "feeling" of the whole scale. The system illustrated above is a "four-shape" system; six of the notes of the scale are grouped