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
Pitch pipe marked the notes of either the chromatic scale or the diatonic scale, and by setting it to the correct position, the indicated note will be produced when the instrument is blown. Pitch pipes come in all sorts of shapes and sizes. Pitch pipes of this sort were most often used in the 18th and 19th centuries in churches which had no organ to give the opening note of a hymn. They are now quite rare, and hardly ever used for what they were intended, but may still be used as an alternative to a tuning fork. They are also useful