SN scale: Difference between revisions
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An SN scale of rank 2, a 2-SN scale, is a [[MOS scale]]. Accordingly, SN scales are a generalization of MOS scales into arbitrary rank. [[ET]]<nowiki/>s can be considered to be 1-SN scales, which can be generated by applying a) once, introducing a step of a single degree of the ET. | An SN scale of rank 2, a 2-SN scale, is a [[MOS scale]]. Accordingly, SN scales are a generalization of MOS scales into arbitrary rank. [[ET]]<nowiki/>s can be considered to be 1-SN scales, which can be generated by applying a) once, introducing a step of a single degree of the ET. | ||
SN scales are [[ | SN scales are [[Rank-3 scales#Rank-2 scales|mirror-symmetric]], and may be uniquely defined by a ''step signature'' - a generalization of the MOS signature into arbitrary rank. | ||
== Examples == | ==Examples == | ||
The diatonic scale can be generated by iterating a) twice, introducing first the octave, then the perfect fifth, and then iterating b) 3 times. It has step signature 5L 2s, and in the symmetric mode, it has step arrangement LsLLLsL. No other arrangement of 5 large and 2 small step sizes results in a SN scale. | The diatonic scale can be generated by iterating a) twice, introducing first the octave, then the perfect fifth, and then iterating b) 3 times. It has step signature 5L 2s, and in the symmetric mode, it has step arrangement LsLLLsL. No other arrangement of 5 large and 2 small step sizes results in a SN scale. | ||
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The simplest 4-SN scale is generated by iterating a) 4 times, leading to the scale abacabad. If we map the intervals introduced with a) as 2/1, 3/2, 7/6, and 15/14, we get the scale 15/14 7/6 5/4 3/2 45/28 7/4 15/8 2/1, with step signature (1,2,4,1), mapped to (6/5, 7/6, 15/14, 16/15). | The simplest 4-SN scale is generated by iterating a) 4 times, leading to the scale abacabad. If we map the intervals introduced with a) as 2/1, 3/2, 7/6, and 15/14, we get the scale 15/14 7/6 5/4 3/2 45/28 7/4 15/8 2/1, with step signature (1,2,4,1), mapped to (6/5, 7/6, 15/14, 16/15). | ||
== Labeling == | ==Labeling== | ||
Where the [[Meantone]] tempered diatonic scale can be labelled as Meantone[7], we may instead describe it through its derivation as an SN scale through labeling it (2/1, 3/2: 81/80)[7], which specifies that a) introduces the intervals 2/1 and 3/2, and then b) is applied until a 7-note scale is reached, and that 81/80 is tempered out in the scale. | Where the [[Meantone]] tempered diatonic scale can be labelled as Meantone[7], we may instead describe it through its derivation as an SN scale through labeling it (2/1, 3/2: 81/80)[7], which specifies that a) introduces the intervals 2/1 and 3/2, and then b) is applied until a 7-note scale is reached, and that 81/80 is tempered out in the scale. | ||
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MET-24, as a (2.3.7.11.13) Parapyth tempered scale can be labelled ((2/1, 3/2)[12], 28/27~33/32: 352/351, 364/363))[24] (the simplest basis set for commas tempered out is chosen to specify the temperament), with step signatures (5, 12, 7) mapped to (~27/26, 28/27~33/32, ~64/63). | MET-24, as a (2.3.7.11.13) Parapyth tempered scale can be labelled ((2/1, 3/2)[12], 28/27~33/32: 352/351, 364/363))[24] (the simplest basis set for commas tempered out is chosen to specify the temperament), with step signatures (5, 12, 7) mapped to (~27/26, 28/27~33/32, ~64/63). | ||
== Further definition == | ==Further definition == | ||
The above scales all have a period of an octave - and therefore a) first introduces the interval of an octave, however, the period of an SN scale, as with the mapping of any new smallest step introduced, is arbitrary. | The above scales all have a period of an octave - and therefore a) first introduces the interval of an octave, however, the period of an SN scale, as with the mapping of any new smallest step introduced, is arbitrary. | ||