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List of set classes

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List of set classes
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This is a list of set classes, by Forte number.[1] In music theory, a set class (an abbreviation of pitch-class-set class) is an ascending collection of pitch classes, transposed to begin at zero. For a list of ordered collections, see this list of tone rows and series.

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Set 3-1 has three possible versions: [01112T], [011TE1], and [0TT1E1], where subscripts indicate adjacency intervals. The normal form is the smallest "slice of pie" (shaded) or most compact form; in this case, [01112T].

Sets are listed with links to their complements. For unsymmetrical sets, the prime form is marked with "A" and the inversion with "B"; sets without either are symmetrical. Sets marked with a "Z" refer to a pair of different set classes with identical interval class content unrelated by inversion, with one of each pair listed at the end of the respective list when they occur. ("Z" is derived from the prefix zygo-, from Ancient Greek ζυγόν, "yoke". Hence: zygosets.) "T" and "E" are conventionally used in sets to notate ten and eleven, respectively, as single characters. The ordering of sets in the lists is based on the string of numerals in the interval vector treated as an integer, decreasing in value, following the strategy used by Forte in constructing his numbering system.

There are two slightly different methods of obtaining the prime form—an earlier one by Allen Forte and a later but now generally more popular one by John Rahn—both often confusingly described as "most packed to the left". However, a more precise description of the Rahn spelling is to select the version most dispersed from the right, whereas the precise description of the Forte spelling is to select the version most packed to the left within the smallest span.[a] In the lists here, the Rahn spelling is used for the 17 out of 352 set classes where the two methods yield different results; the alternative Forte spellings are listed in the footnotes.[3][4]

Before either (1960–67), Elliott Carter had produced a numbered listing of pitch class sets, or "chords", as Carter referred to them, for his own use.[5][6] Donald Martino had produced tables of hexachords, tetrachords, trichords, and pentachords for combinatoriality in his 1961 article, "The Source Set and its Aggregate Formations".[7]

The difference between the interval vectors of a set and its complement is <X, X, X, X, X, X/2>, where (in base-ten) X = 12 – 2C, where C is the smaller set's cardinality. In nearly all cases, complements of unsymmetrical sets are related by inversion—i.e., the complement of an "A" version of a set of cardinality C is (usually) the "B" version of the respective set of cardinality 12 – C. The most significant exceptions are the sets 4-14/8-14, 5-11/7-11, and 6-14, which are all closely related in terms of subset/superset structure.

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More information Forte no., Prime form ...

There is an anomaly in Allen Forte's book concerning the numbering of the pair of hexachords 6-Z28, [011232516393], and 6-Z49, [011231437293], where adjacency intervals are shown here by subscripts. They both have the same span, with a minor-third at the right. But, within that span, the hexachord [0,1,3,4,7,9] is "more packed to the left" than [0,1,3,5,6,9], as seen by inspecting the left-hand adjacency-interval sequences, and therefore, according to Forte's own rule, the set [0,1,3,4,7,9] should have been assigned the lower number 6-Z28, with [0,1,3,5,6,9] given the higher number 6-Z49.

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