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
Quarter note Quarter note A quarter note (American) or crotchet (British) is a note played for one quarter of the duration of a whole note (or semibreve). Often, musicians will say that a crotchet is one beat, but this is not always correct, as the beat is indicated by the time signature of the music; a quarter note may or may not be the beat. Quarter notes are notated with a filled-in oval note head and a straight, flagless stem. The stem usually points upwards if it is below the middle line of the stave or downwards if it is on or