Musical notation its "natural" form, which means that any sharps or flats applying to that note from the key signature or from accidentals are cancelled. Sometimes a courtesy accidental is used in music where it is not technically required, to remind the musician of what pitch the key signature requires. Following the key signature is the time signature. The time signature typically consists of two numbers, with one of the most common being "4/4". The top "4" indicates that there are four beats per measure (also called bar). The bottom "4" indicates that each of those beats are quarter notes. Measures divide
Key signature use may be found in Klezmer scales, such as Freygish (Phrygian). In the 20th century, composers such as Bartók and Rzewski (see below) began experimenting with unusual key signatures that departed from the standard order. Because of the limitations of the traditional highland bagpipe scale, key signatures are often omitted from written pipe music, which otherwise would be written with two sharps, the usual F and C. (In this case the pipes are incapable of playing F and C so it is not necessary to specify the sharps.) The above 15 key signatures only express diatonic scale. and are therefore