Interval of equivalence: Difference between revisions
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* [[Stretched tuning]] | * [[Stretched tuning]] | ||
* [[Equave limit]] | * [[Equave limit]] | ||
== Mathematical interpretation == | |||
If intervals and notes an equave apart are considered to be wholly equivalent to one another, and are collapsed down to a single representative interval (as is usually the case when constructing lattices), this is mathematically identical to [[tempering out]] the equave, as it is an interval separating notes that are treated as the same thing. This gives us a tool to formalize the notion of equivalence in the language of regular temperament theory - for example, octave-equivalent meantone is a rank-1 temperament that tempers out 81/80, but also "tempers out" 2/1. | |||
== Notes == | == Notes == | ||
Revision as of 00:08, 24 April 2025
The equave (/ˈiːkwɪv/ EE-kwiv or /ˈiːkwəv/ EE-kwəv), also called interval of equivalence, equivalence interval, formal octave[1][note 1]or pseudo-octave[2][note 1], is the interval such that pitches separated by it are considered psychoacoustically or formally equivalent and are elements of the same pitch class.
If a periodic scale has an equave, the equave is typically the same as the period or a multiple thereof.
Etymology
The term equave was coined by Inthar. It is a portmanteau of equivalence and octave.
Examples
- In octave-repeating scales, the equave is typically 2/1.
- In Bohlen–Pierce, the equave may be taken as 3/1.
- In edfs, the equave may be taken as 3/2 or less commonly 9/4.
See also
Mathematical interpretation
If intervals and notes an equave apart are considered to be wholly equivalent to one another, and are collapsed down to a single representative interval (as is usually the case when constructing lattices), this is mathematically identical to tempering out the equave, as it is an interval separating notes that are treated as the same thing. This gives us a tool to formalize the notion of equivalence in the language of regular temperament theory - for example, octave-equivalent meantone is a rank-1 temperament that tempers out 81/80, but also "tempers out" 2/1.
Notes
- ↑ 1.0 1.1 The terms formal octave and pseudo-octave are often used specifically to designate a stretched or compressed octave, but they may more generally designate any kind of equave.
References
- ↑ Op de Coul, E.F. Scala help.
- ↑ ASCL Specification. Ableton.