Editing Key signature (section)

== Use in other traditions <span class="anchor" id="Use outside of the Western common-practice period"></span> ==<!--[[Unusual key signature]] redirects directly here.-->

{{Image frame|content=<score>{
\relative c' {
  \set Staff.keyAlterations = #`((6 . ,FLAT)(2 . ,FLAT)(3 . ,SHARP)) d es fis g a bes c d }}</score>|width=270|caption=D [[Phrygian dominant scale|Freygish]] scale {{audio|D Freygish.mid|Play}}}}

Key signatures are also used in music that does not come from the Western [[common practice period]]. This includes folk music, non-Western music, and Western music from before or after the common practice period.

[[Klezmer]] music uses scales other than diatonic major or minor, such as [[Phrygian dominant scale]]. Because of the limitations of the [[Great Highland Bagpipe]] scale, key signatures are often omitted from written pipe music, which otherwise would be written with two sharps, F{{music|#}} and C{{music|#}}.<ref>
{{cite web |url=http://lilypond.org/doc/v2.12/Documentation/user/lilypond/Bagpipes#Bagpipes |title=GNU LilyPond—Notation Reference |last1=Nienhuys |first1=Han-Wen |last2=Nieuwenhuizen |first2=Jan |author-link1=Han-Wen Nienhuys |author-link2=Jan Nieuwenhuizen |year=2009 |at=2.6.2 Bagpipes |access-date=2010-03-28 |quote=Bagpipe music nominally uses the key of D Major (even though that isn’t really true). However, since that is the only key that can be used, the key signature is normally not written out.}}</ref> (The pipes are incapable of playing F{{music|natural}} and C{{music|natural}} so the sharps are not notated.) 20th century composers such as [[Béla Bartók|Bartók]] and [[Frederic Rzewski|Rzewski]] (see below) experimented with non-diatonic key signatures.

=== Historical notation ===
[[File:Earlykeysig.png|thumb|right|80px|Variant key signatures in a [[Tomas Luis de Victoria|Victoria]] motet. In the ''superius'' (soprano) part the E{{music|flat}} appears first, and in two other parts a flat occurs in two octaves.]]

In music from the Baroque period, it is common to see key signatures in which the notes are annotated in a different order from the modern practice, or with the same note-letter annotated for each octave.

=== Unusual signatures ===
{{further information|Anhemitonic scale#Modes of the ancohemitonic heptatonic scales and the key signature system}}

The 15 key signatures that form diatonic scales are sometimes called ''standard key signatures''. Other scales are written either with a standard key signature and use accidentals as required, or with a nonstandard key signature. Examples of the latter include the E{{music|b}} (right hand), and F{{music|#}} and G{{music|#}}<!--yes, sharp--> (left hand) used for the С diminished (С [[octatonic scale|octatonic]]) scale in Bartók's ''Crossed Hands'' (no. 99, vol. 4, ''[[Mikrokosmos (Béla Bartók)|Mikrokosmos]]''); the B{{music|b}}, E{{music|b}} and F{{music|#}}<!--yes, sharp--> used for the D [[Phrygian dominant scale]] in [[Frederic Rzewski]]'s ''God to a Hungry Child''; and the E{{music|b}} and D{{music|b}} (right hand) and the B{{music|b}}, A{{music|b}}, G{{music|b}} (left hand) in [[György Ligeti]]'s ''Galamb Borong'' (no. 7 from the second book  of the ''Études pour piano''), and B{{music|b}}, E{{music|b}}, D{{music|b}}, G{{music|b}} (both hands) in ''Pour Irina'' (no. 16 from the same work's third book).

There are also examples of conflicting standard signatures, as in:
* no. 3 of [[Sergei Prokofiev]]'s ''[[Sarcasms (Prokofiev)|Sarcasms]]'', op. 17 (three sharps in the right hand, and five flats in the left hand)
* and four numbers of [[György Ligeti|Ligeti]]'s ''[[Études (Ligeti)|Études pour piano]]'':
** no. 1 from the first book (none in the right hand, and five sharps in the left hand)
** no. 10 from the second book (''Der Zauberlehrling''; none in the right hand, and five flats in the left hand in bars 67–87)
** no. 11 from the second book (''En Suspens''; five flats in the right hand and none in the left hand, with the opposite later on)
** no. 12 from the second book (''Entrelacs''; none in the right hand and five flats in the left hand, with the opposite later on)

No sharps or flats in a key signature can indicate that the music is in the key of C major&nbsp;/ A minor, or that the piece is [[Musical mode|modal]] or [[atonality|atonal]] (does not have a key signature). An example is Bartók's [[Piano Sonata (Bartók)|Piano Sonata]], which has no fixed key and is highly chromatic.