ELD: Difference between revisions

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address Flora's recent concerns about rationality vs. irrationality in this system
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An '''ELD''', or '''equal length division''', is a kind of [[Arithmetic tunings|arithmetic]] and [[Harmonotonic tunings|harmonotonic]] tuning.
An '''ELD''' ('''equal length division'''), '''ALD''' ('''arithmetic length division'''), or '''IFD''' ('''inverse-arithmetic frequency division'''), is an [[Arithmetic tunings|arithmetic]] and [[period]]ic [[tuning]] in which each period is divided to a number of steps of equal length difference.  


== Specification ==
== Specification ==


Its full specification is n-ELDp: n equal length divisions of the interval p.  
Its full specification is ''n''-ELD-''p'' (''n'' equal length divisions of ''p''), or ''n''-ALD-''p'' (''n'' arithmetic length divisions of ''p''), or ''n''-IFD-''p'' (''n'' inverse-arithmetic frequency division of ''p'').  


== Formula ==
== Formula ==


To find the steps for an n-ELDp, begin by recognizing that while the ratio between your root pitch's string length and the length you would pluck to get the lowest pitch is <span><math>p</math></span> (or <span><math>\frac p1</math></span>), if you are going to move arithmetically (by repeated addition) from <span><math>1</math></span> to <span><math>p</math></span>, then the difference in string length that you need to cover is not actually <span><math>p</math></span>, but only <span><math>p - 1</math></span>. And because you are dividing it into <span><math>n</math></span> parts, each step will have a size of <span><math>\frac{p-1}{n}</math></span>. So, the formula for the length of step <span><math>k</math></span> of an n-ELDp is:
To find the steps for an ''n''-ELD-''p'', begin by recognizing that while the ratio between your root pitch's string length and the length you would pluck to get the lowest pitch is <span><math>p</math></span> (or <span><math>\frac p1</math></span>), if you are going to move arithmetically (by repeated addition) from <span><math>1</math></span> to <span><math>p</math></span>, then the difference in string length that you need to cover is not actually <span><math>p</math></span>, but only <span><math>p - 1</math></span>. And because you are dividing it into <span><math>n</math></span> parts, each step will have a size of <span><math>\frac{p-1}{n}</math></span>. So, the formula for the length of step <span><math>k</math></span> of an n-ELDp is:


<math>
<math>
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=== Vs. UD ===
=== Vs. UD ===


The only difference between an n-ELDp and an [[UD|n-UDp (or utonal division)]] is that the p for a utonal division must be rational.
An [[UD|''n''-UD-''p'' (or utonal division)]] is equivalent to an ''n''-ELD-''p'' except that the period ''p'' of the UD must be rational.


=== Vs. EFD ===
=== Vs. EFD ===
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=== Vs. ALS ===
=== Vs. ALS ===


One period of an ELD will be equivalent to some [[ALS|ALS (arithmetic length sequence)]]; specifically n-ELD((p-1)/n) = n-ALSp.
One period of an ELD will be equivalent to some [[ALS|ALS (arithmetic length sequence)]]; specifically ''n''-ELD((''p'' - 1)/''n'') = ''n''-ALS-''p''.


=== Vs. EDL ===
=== Vs. EDL ===
Retrieved from "https://en.xen.wiki/w/ELD"