Temperament addition: Difference between revisions

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'''Temperament arithmetic''' is the general name for either the '''temperament sum''' or the '''temperament difference''', which are two closely related operations on [[regular temperaments]]. Basically, to do temperament arithmetic means to match up the entries of temperament vectors and then add or subtract them individually. The result is a new temperament that has similar properties to the original temperaments.
'''Temperament arithmetic''' is the general name for either the '''temperament sum''' or the '''temperament difference''', which are two closely related operations on [[regular temperaments]]. Basically, to do temperament arithmetic means to match up the entries of temperament vectors and then add or subtract them individually. The result is a new temperament that has similar properties to the original temperaments.


For example, the sum of [[12-ET]] and [[7-ET]] is [[19-ET]] because {{map|12 19 28}} + {{map|7 11 16}} = {{map|(12+7) (19+11) (28+16)}} = {{map|19 30 44}}, and the difference of 12-ET and 7-ET is 5-ET because {{map|12 19 28}} - {{map|7 11 16}} = {{map|(12-7) (8-11) (12-16)}} = {{map|5 8 12}}. We can write these using [[wart notation]] as 12p + 7p = 19p and 12p - 7p = 5p, respectively. The similarity in these temperaments can be seen in how, like both 12-ET and 7-ET, 19-ET also supports [[meantone temperament]].
For example, the sum of [[12-ET]] and [[7-ET]] is [[19-ET]] because {{map|12 19 28}} + {{map|7 11 16}} = {{map|(12+7) (19+11) (28+16)}} = {{map|19 30 44}}, and the difference of 12-ET and 7-ET is 5-ET because {{map|12 19 28}} - {{map|7 11 16}} = {{map|(12-7) (8-11) (12-16)}} = {{map|5 8 12}}. We can write these using [[wart notation]] as 12p + 7p = 19p and 12p - 7p = 5p, respectively. The similarity in these temperaments can be seen in how, like both 12-ET and 7-ET, 19-ET (their sum) and 5-ET (their difference) both also support [[meantone temperament]].


Temperament sums and differences can also be found using commas; for example meantone + porcupine = tetracot because {{vector|4 -4 1}} + {{vector|1 -5 3}} = {{vector|(4+1) (-4+-5) (1+3)}} = {{vector|5 -9 4}} and meantone - porcupine = dicot because {{vector|4 -4 1}} - {{vector|1 -5 3}} = {{vector|(4-1) (-4--5) (1-3)}} = {{vector|3 1 -2}}. We could write this in ratio form — replacing addition with multiplication and subtraction with division — as 80/81 × 250/243 = 20000/19683 and 80/81 ÷ 250/243 = 25/24, respectively. The similarity in these temperaments can be seen in how all of them are supported by 7-ET.
Temperament sums and differences can also be found using commas; for example meantone + porcupine = tetracot because {{vector|4 -4 1}} + {{vector|1 -5 3}} = {{vector|(4+1) (-4+-5) (1+3)}} = {{vector|5 -9 4}} and meantone - porcupine = dicot because {{vector|4 -4 1}} - {{vector|1 -5 3}} = {{vector|(4-1) (-4--5) (1-3)}} = {{vector|3 1 -2}}. We could write this in ratio form — replacing addition with multiplication and subtraction with division — as 80/81 × 250/243 = 20000/19683 and 80/81 ÷ 250/243 = 25/24, respectively. The similarity in these temperaments can be seen in how all of them are supported by 7-ET.