Editing Circle of fifths (section)

== Definition ==
The circle of fifths organizes pitches in a sequence of [[perfect fifth]]s, generally shown as a circle with the pitches (and their corresponding keys) in clockwise order. It can be viewed in a counterclockwise direction as a circle of fourths. Harmonic progressions in Western music commonly use adjacent keys in this system, making it a useful reference for musical composition and harmony.<ref>Michael Pilhofer and Holly Day (23 Feb 2009). [http://www.dummies.com/how-to/content/the-circle-of-fifths-a-brief-history.html "The Circle of Fifths: A Brief History"], www.dummies.com.</ref>

The top of the circle shows the [[Key (music)|key]] of C Major, with no [[Sharp (music)|sharps]] or [[Flat (music)|flats]]. Proceeding clockwise, the pitches ascend by fifths. The key signatures associated with those pitches change accordingly: the key of G has one sharp, the key of D has 2 sharps, and so on. Proceeding counterclockwise from the top of the circle, the notes change by descending fifths and the key signatures change accordingly: the key of F has one flat, the key of B{{music|flat}} has 2 flats, and so on. Some keys (at the bottom of the circle) can be notated [[Enharmonic|either in sharps or in flats]].

Starting at any pitch and ascending by a fifth generates all tones before returning to the beginning pitch class (a pitch class consists of all of the notes indicated by a given letter regardless of octave—all "C"s, for example, belong to the same pitch class). Moving counterclockwise, the pitches descend by a fifth, but ascending by a [[perfect fourth]] will lead to the same note an octave higher (therefore in the same pitch class). Moving counter-clockwise from C could be thought of as descending by a fifth to F, or ascending by a fourth to F.
{{col-begin}}
{{col-break}}
{{Image frame|content=<score sound="1"> {
\omit Score.TimeSignature
\relative c' { \set Score.tempoHideNote = ##t \tempo 1 = 60 \time 12/1
  c1 g' d a' e b' fis cis gis' dis ais' f | c! \bar "|."
} }
\layout { \context {\Score \omit BarNumber} line-width = #100 }
</score>|width=|align=center|caption=Circle of fifths clockwise within one octave}}
{{col-break}}
{{Image frame|content=<score sound="1">  {
\omit Score.TimeSignature
\relative c' { \set Score.tempoHideNote = ##t \tempo 1 = 60 \time 12/1
  c1 f bes ees, aes des, ges b e, a d, g | c, \bar "|."
} }
\layout { \context {\Score \omit BarNumber} line-width = #100 }
</score>|width=|align=center|caption=Circle of fifths counterclockwise within one octave}}
{{col-end}}