Editing Key signature (section)

== Relationship between key and signature ==
The sharps or flats needed to produce a [[diatonic scale]] in [[diatonic]] or [[tonality|tonal]] music can be shown as a key signature at the beginning of a section of music instead of showing accidentals on individual notes. While the key of a piece generally corresponds to the notated key signature, it may not in some cases, such as in pre-Baroque music, which was composed before the modern concept of keys had fully emerged.

Some pieces feature [[modulation (music)|modulation]]s, or changes in key, between contrasting sections. Modulations may or may not be reflected by a corresponding change in key signature. Modulated passages may instead make use of accidentals.

[[File:GottesZeit.png|400px|thumb|right|[[Gottes Zeit ist die allerbeste Zeit, BWV 106|Bach Cantata 106]] is almost entirely in E{{music|flat}} major, but has only two flats, not three, in the key signature {{audio|GottesZeit.mid|Play}}]]

The [[Toccata and Fugue in D minor, BWV 538]] by [[Johann Sebastian Bach|Bach]] has a key signature with no sharps or flats, indicating that it may be in D, in [[Dorian mode]], but the B{{music|flat}}s indicated with [[Accidental (music)|accidentals]] make the music in D minor.

===Additional terminology===
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Keys which are associated with the same key signature are called [[relative minor/major|relative keys]].

When [[musical mode]]s, such as [[Lydian mode|Lydian]] or Dorian, are written using key signatures, they are called ''transposed modes''.