Period: Difference between revisions

Improve lead section, add "Scale types" section (not sure about the title, good enough for now), enclose last part into an "Examples" section, categories
Move non-periodic scales at the bottom of the page, rephrase its definition to lessen the impression that the term is common.
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The '''period''' (or '''interval of repetition''') of a [[scale]] is the [[interval]] at which the scale's [[step pattern]] eventually repeats, if it does at all.
The '''period''' (or '''interval of repetition''') of a [[scale]] is the [[interval]] at which the scale's [[step pattern]] eventually repeats, if it does at all. In practice, the period often corresponds to the [[equave]] (interval of equivalence) or to a fraction of the equave.


In practice, the period often corresponds to the [[equave]] (interval of equivalence) or to a fraction of the equave.
A ''[[periodic scale]]'' is a scale whose step pattern always repeats after a certain number of steps. The [[diatonic scale]] is an example of periodic scale.
 
An ''aperiodic scale'' is a scale whose step pattern never repeats. The [[harmonic series]] is an example of aperiodic scale.


In [[regular temperament theory]], the period of a scale always coincides with one of its generators.
In [[regular temperament theory]], the period of a scale always coincides with one of its generators.
== Scale types ==
* A ''[[periodic scale]]'' is a scale whose step pattern always repeats after a certain number of steps. The [[diatonic scale]] is an example of periodic scale.
* A ''non-periodic scale'' is a scale whose step pattern does not systematically repeat, but that may have small repeating segments in its step pattern. This type of scale is less common, but technically includes any scale with a finite number of notes and which is not expected to repeat at all, such as the sequence of {{w|DTMF}} tones.
* An ''aperiodic scale'' is a scale whose step pattern never repeats. The [[harmonic series]] is an example of aperiodic scale.


== Examples ==
== Examples ==
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The same definition applies for a [[rank]]-2 temperament, when the temperament is seen as generating a mos. Every interval of a rank-2 temperament is a sum of some number of the period and some number of the generator of the temperament.
The same definition applies for a [[rank]]-2 temperament, when the temperament is seen as generating a mos. Every interval of a rank-2 temperament is a sum of some number of the period and some number of the generator of the temperament.
== Special cases ==
A scale whose step pattern does not systematically repeat, but that may have small repeating segments in its step pattern, may be called a ''non-periodic scale''. This type of scale is less common, but technically includes any scale with a finite number of notes and which is not expected to repeat at all, such as the sequence of DTMF tones. Aperiodic scales are a subset of non-periodic scales.


[[Category:Scale]]
[[Category:Scale]]
[[Category:Generator]]
[[Category:Generator]]
[[Category:Terms]]
[[Category:Terms]]