Frequency temperament: Difference between revisions

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A standard [[rank-2 temperament]] has a generator interval and a period interval, and new intervals are produced by taking powers of the generator, and then reducing them logarithmically to the range from [[1/1]] to the period. But in arithmetic temperaments, new intervals are produced by taking ''multiples'' of the generator and reducing them arithmetically.
A standard [[rank-2 temperament]] has a generator interval and a period interval, and new intervals are produced by taking powers of the generator, and then reducing them logarithmically to the range from [[1/1]] to the period. But in arithmetic temperaments, new intervals are produced by taking ''multiples'' of the generator and reducing them arithmetically.


For example, consider an arithmetic temperament with generator [[9/7]] and period [[2/1]]. If we want to add a third interval, then multiply 9/7 by 2 to obtain 18/7. Since 18/7 is greater than an octave, subtract 1 to get [[11/7]]. To get a fourth interval, multiply 9/7 by 3 to get 27/7, then subtract 2 to get [[13/7]]. In contrast to a logarithmic rank-2 temperament, we can only produce 7 intervals this way (creating [[7ado]]) before the intervals will start repeating.
For example, consider an arithmetic temperament with a generator of 1.29 (440 cents) and period [[2/1]]. If we want to add a third interval, multiply 1.29 by 2 to obtain 2.58. Since 2.58 is outside of an octave, subtract 1 to get 1.58. To add a fourth interval, multiply 1.29 by 3 and subtract 2 to get 1.87. We can continue generating new intervals this way like in a normal rank-2 temperament.