Equiheptatonic

Equiheptatonic scales are heptatonic scales with 7 roughly equally spaced tones per octave.

They are usually not exactly equally spaced, but deviate from equal by small amounts, often to improve the tuning of 3/1 and 5/1.

Musical traditions that make use of equiheptatonic scales include:

• Eastern Angolan music
• Cambodian classical music
• Ancient Greek auloi music
• Laotian classical music
• Thai classical music
• Vietnamese classical music
• Lower Zambezi music
  • Nyungwe music

Note that just because a tradition has an equiheptatonic scale doesn’t mean it uses it exclusively. They often have other tunings too. Also, the term “scale” here is used loosely, because many, perhaps the majority, of musical traditions don’t use scales, but use something else like tetrachords, raag, etc. that scales can only loosely model.

An exactly equal equiheptatonic scale equals 7edo, which is popular with modern Western xenharmonic composers.