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
C (musical note) C (musical note) C (Italian, French: "Do") is the first note of the C major scale, the third note of the A minor scale (the relative minor of C major), and the fourth note (F, A, B, C) of the Guidonian hand, commonly pitched around 261.63 Hz. The actual frequency has depended on historical pitch standards, and for transposing instruments a distinction is made between written and sounding or concert pitch. In English the term "Do" is used interchangeably with C only by adherents of fixed-Do solfège; in the movable Do system Do refers to the tonic of the prevailing