Interval system: Difference between revisions
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Another type of open system can be infinite even if its pitches occupy a finite frequency range, because it is defined by a rule for generating successive intervals under which, no matter how many times the generative process is repeated, no new interval is ever identical to a previous interval. An example of this is 3-prime-limit JI, a musical interval system in which intervals are generated by successive combinations of the 2nd and 3rd harmonics. Another example would be any of the golden horagrams of Erv Wilson. | Another type of open system can be infinite even if its pitches occupy a finite frequency range, because it is defined by a rule for generating successive intervals under which, no matter how many times the generative process is repeated, no new interval is ever identical to a previous interval. An example of this is 3-prime-limit JI, a musical interval system in which intervals are generated by successive combinations of the 2nd and 3rd harmonics. Another example would be any of the golden horagrams of Erv Wilson. | ||
Among open systems, the most important kinds are [[ | Among open systems, the most important kinds are [[periodic scale]]s and group systems. The latter refers to "groups" in the mathematical sense of [http://en.wikipedia.org/wiki/Abelian_group abelian groups], and means that you are always allowed to invert intervals, and that given any two intervals, you may combine them. | ||
Examples of group systems are all positive real numbers under multiplication, regarded as frequencies in hertz; all real numbers under addition, regarded as intervals in cents; all positive rational numbers, regarded as intervals from a chosen 1/1; all rational numbers in a given [[ | Examples of group systems are all positive real numbers under multiplication, regarded as frequencies in hertz; all real numbers under addition, regarded as intervals in cents; all positive rational numbers, regarded as intervals from a chosen 1/1; all rational numbers in a given [[harmonic limit]]; all intervals in a [[Just intonation subgroups|just intonation subgroup]]; and all intervals in a [[Regular Temperaments|regular temperament]]. | ||
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