Key signature may consist of one or more sharps combined with one or more flats (such as a signature containing both F and B). Key signatures of this kind can be found in the music of Béla Bartók, for example. The effect of a key signature continues throughout a piece or movement, unless explicitly cancelled by another key signature. For example, if a five-sharp key signature is placed at the beginning of a piece, every A in the piece in any octave will be played as A sharp, unless preceded by an accidental (for instance, the A in scale 2 illustrated –
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