Musical note indicated by placing the symbols in the key signature, which then apply implicitly to all occurrences of corresponding notes. Explicitly noted accidentals can be used to override this effect for the remainder of a bar. A special accidental, the natural symbol , is used to indicate an unmodified pitch. Effects of key signature and local accidentals do not accumulate. If the key signature indicates G, a local flat before a G makes it G (not G), though often this type of rare accidental is expressed as a natural, followed by a flat () to make this clear. Likewise (and more
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