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
E (musical note) in pieces where E is in the key signature, in order to represent a diatonic, rather than a chromatic semitone; writing an E with a following E is regarded as a chromatic alteration of one scale degree. E (musical note) E is the third note of the C major scale, and mi in fixed-do solfège. It has enharmonic equivalents of F♭ (which is by definition a diatonic semitone above E) and D, amongst others. When calculated in equal temperament with a reference of A above middle C as 440 Hz, the frequency of Middle E (E) is approximately 329.628 Hz.