Editing Octatonic scale (section)

==Construction==
{{Image frame|content=<score sound="1">
{
\override Score.TimeSignature #'stencil = ##f
\relative c' {
  \clef treble \key c \major \time 8/4
  es4 f fis gis a b c d es2
} }
</score>

<score sound="1">
{
\override Score.TimeSignature #'stencil = ##f
\relative c' {
  \clef treble \key c \major \time 8/4
  d4 e f g gis ais b cis d2
} }
</score>

<score sound="1">
{
\override Score.TimeSignature #'stencil = ##f
\relative c' {
  \clef treble \key c \major \time 8/4
  cis4 dis e fis g a bes c cis2
} }
</score>|width=300|caption=The three octatonic scales}}The twelve tones of the chromatic scale are covered by three disjoint [[diminished seventh chord]]s. The <!-- union of the --> notes from two such seventh-chords combination form an octatonic collection. Because there are three ways to select two from three, there are three octatonic scales in the twelve-tone system.

Each octatonic scale has exactly two [[mode (music)|modes]]: the first begins its ascent with a [[major second|whole step]], while the second begins its ascent with a half step ([[semitone]]). These modes are sometimes referred to as the ''whole step/half-step diminished scale'' and the ''half-step/whole step diminished scale'', respectively.{{sfn|Levine|1995|loc=78}}

Each of the three distinct scales can form differently named scales with the same sequence of tones by starting at a different point in the scale. With alternative starting points listed below in square brackets, and return to tonic in parentheses, the three are, ascending by semitones:

* C{{music|sharp}} D{{music|sharp}} [E] F{{music|sharp}} [G] A [A{{music|sharp}}] B{{music|sharp}} (C{{music|sharp}})
* D E [F] G [G{{music|sharp}}] A{{music|sharp}} [B] C{{music|sharp}} (D)
* E{{music|flat}} F [G{{music|flat}}] A{{music|flat}} [A{{music|natural}}] B [C] D (E{{music|flat}})

It may also be represented as semitones, either starting with a whole tone (as above): {{nowrap|0 2 3 5 6 8 9 11 (12)}}, or starting with a semitone: {{nowrap|0 1 3 4 6 7 9 10 (12)}}, or labeled as [[set class]]&nbsp;8‑28.{{sfn|Schuijer|2008|loc=109}}

With one more scale tone than described by the western [[diatonic scale]], it is not possible to perfectly notate music of the octatonic scale using any conventional [[key signature]] without the use of accidentals. Across all conventional key signatures, at least two of the octatonic notes must share similar horizontal alignment on the [[staff (music)|staves]], although the precise combination of accidentals and naturals varies. There are usually several equally succinct combinations of key signature and accidentals, and different composers have chosen to notate their music differently, sometimes ignoring the niceties of notation conventions designed to facilitate [[diatonic]] [[tonality]].