Editing Heptatonic scale (section)

==Heptatonia prima and secunda==
The names ''heptatonia prima'' and ''heptatonia secunda'' apply to seven-note scales that can be formed using five [[whole tone|tones]] (t) and two [[semitone|semi-tones]] (s), (also called whole-steps and half-steps), but without two semi-tones in succession. Throughout history and to the present day, some have occurred much more commonly than others, namely Ionian (also called the major scale), Aeolian (also called the natural minor scale), melodic ascending minor, Dorian, Mixolydian, Lydian, Lydian dominant, Aeolian dominant, and altered scales.

===Heptatonia prima===
In these scales the semi-tones are maximally separated. They are known most commonly as the [[diatonic]] modes. Beginning on keynote C and working up the notes of the 'major' scale (C, D, E, F, G, A, B, C), the seven modes are:
[[Image:Ionian mode C.png|thumb|left|Ionian mode C {{audio|Ionian mode C.mid|Play}}]]
* [[Ionian mode]] (major) t-t-s-t-t-t-s
[[Image:Dorian mode C.png|thumb|right|Dorian mode C {{audio|Dorian mode C.mid|Play}}]]
* [[Dorian mode]] t-s-t-t-t-s-t
[[Image:Phrygian mode C.png|thumb|left|Phrygian mode C {{audio|Phrygian mode C.mid|Play}}]]
* [[Phrygian mode]] s-t-t-t-s-t-t
[[Image:Lydian mode C.png|thumb|right|Lydian mode C {{audio|Lydian mode C midi.mid|Play}}]]
* [[Lydian mode]] t-t-t-s-t-t-s
[[Image:Mixolydian mode C.png|thumb|left|Mixolydian mode C. {{audio|Mixolydian mode C.mid|Play}}]]
* [[Mixolydian mode]] t-t-s-t-t-s-t
[[Image:Aeolian mode C.png|thumb|left|Aeolian mode C {{audio|Aeolian mode C.mid|Play}}]]
* [[Aeolian mode]] (natural minor) t-s-t-t-s-t-t
[[Image:Locrian mode C.png|thumb|right|Locrian mode C {{audio|Locrian mode C.mid|Play}}]]
* [[Locrian mode]] s-t-t-s-t-t-t

===Heptatonia secunda===
While the diatonic modes have two and three tones on either side of each semitone, the heptatonia secunda modes have one and four.
These are sometimes called modes of the melodic ascending minor since that is the most commonly used scale of this type, but other modes can be produced by starting on the different scale notes in turn.
Thus starting on keynote A as above and following the notes of the ascending melodic minor (A, B, C, D, E, F{{music|sharp}}, G{{music|sharp}}) yields these seven modes:

[[Image:Amoll.melod.auf.png|thumb|right|Ascending melodic minor scale on A {{audio|Amoll melod auf.mid|Play}}]]
* [[Ascending melodic minor scale]] t-s-t-t-t-t-s
* [[Dorian ♭2 scale]] or Phrygian {{music|sharp}}6 scale s-t-t-t-t-s-t combines the Phrygian flat second and Dorian raised sixth
* [[Lydian augmented scale]] t-t-t-t-s-t-s combines the Lydian fourth with a raised fifth
[[Image:Lydian dominant C.png|thumb|left|Acoustic scale on C. {{audio|Lydian dominant C.mid|Play}}]]
* [[Acoustic scale]] or Lydian dominant scale t-t-t-s-t-s-t So-called because it is close to the scale built on natural overtones and combines Lydian raised fourth with Mixolydian (Dominant) flat seventh
* [[Aeolian dominant scale]] or Mixolydian {{music|flat}}6 scale t-t-s-t-s-t-t Like natural minor (aeolian) but with a major third
[[Image:Half diminished scale C.png|thumb|right|Half diminished scale on C {{audio|Half diminished scale C.mid|Play}}]]
* [[Half diminished scale]] t-s-t-s-t-t-t This is like the Locrian with a raised second
[[Image:C altered scale flats.png|thumb|left|Altered scale on C {{audio|Altered scale on C.mid|Play}}]]
* [[Altered scale]] s-t-s-t-t-t-t Like Locrian with diminished fourth

These modes are more awkward to use than those of the diatonic scales due to the four tones in a row yielding augmented intervals on one hand while the one tone between two semitones gives rise to diminished intervals on the other. For example, the last two modes listed above both have 'Locrian' diminished triads built on their tonics, giving them unstable tonality, while the third mode not only has an augmented fourth a la the Lydian mode but also an augmented fifth making the dominant and subdominant essentially unusable.