Pergen names: Difference between revisions
Wikispaces>TallKite **Imported revision 621914201 - Original comment: ** |
Wikispaces>TallKite **Imported revision 621915379 - Original comment: ** |
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<h2>IMPORTED REVISION FROM WIKISPACES</h2> | <h2>IMPORTED REVISION FROM WIKISPACES</h2> | ||
This is an imported revision from Wikispaces. The revision metadata is included below for reference:<br> | This is an imported revision from Wikispaces. The revision metadata is included below for reference:<br> | ||
: This revision was by author [[User:TallKite|TallKite]] and made on <tt>2017-11-18 | : This revision was by author [[User:TallKite|TallKite]] and made on <tt>2017-11-18 09:12:20 UTC</tt>.<br> | ||
: The original revision id was <tt> | : The original revision id was <tt>621915379</tt>.<br> | ||
: The revision comment was: <tt></tt><br> | : The revision comment was: <tt></tt><br> | ||
The revision contents are below, presented both in the original Wikispaces Wikitext format, and in HTML exactly as Wikispaces rendered it.<br> | The revision contents are below, presented both in the original Wikispaces Wikitext format, and in HTML exactly as Wikispaces rendered it.<br> | ||
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For non-standard prime groups, the period uses the first prime only, and the multi-gen uses the first two primes only. [[Kite's color notation|Color notation ]]is used to indicate primes higher than 3. For example, 2.5.7 with 50/49 tempered out is {P8/2, y3} = half-octave, yellow-third. | For non-standard prime groups, the period uses the first prime only, and the multi-gen uses the first two primes only. [[Kite's color notation|Color notation ]]is used to indicate primes higher than 3. For example, 2.5.7 with 50/49 tempered out is {P8/2, y3} = half-octave, yellow-third. | ||
Rank-3 pergen | Rank-3 pergen sets have three intervals, any of which may be split. The unsplit 2.3.5... subgroup is {P8, P5, y3} = fifth-and-third-based. 2.3.5.7 with 50/49 tempered out is {P8/2, P5, y3}. | ||
Rank-4 temperaments | Rank-4 temperaments have pergen sets of four intervals. Rank-1 temperaments could have pergen sets of one, such as {P8/12} for 12-edo or {P12/13} for 13-ed3, but there's no particular reason to do so. | ||
To find a temperament's pergen set, first find the PGM, the period generator mapping. This is a matrix with a column for each prime in the subgroup, and a row for each generator, counting the period as a special type of generator. Choose your generators so that all entries below the diagonal are zero. (This is not a problem with rank-2 temperaments.) You can use x31.com to find this matrix. Next make a square matrix by discarding columns for the higher primes. Then invert the matrix to get the monzos for each generator. Add/subtract periods from the generator to get alternate generators. Add/subtract both periods and generators from the 2nd generator to get more alternates. Choose the alternates to minimize the splitting and the cents. | |||
Example: 2.3.5.7 with 2401/2400 = (-5,-1,-2,4) tempered out. x31.com gives us this matrix: | |||
||~ ||~ 2/1 ||~ 3/1 ||~ 5/1 ||~ 7/1 || | |||
||~ period ||= 1 ||= 1 ||= 1 ||= 2 || | |||
||~ gen1 ||= 0 ||= 2 ||= 1 ||= 1 || | |||
||~ gen2 ||= 0 ||= 0 ||= 2 ||= 1 || | |||
Thus 2/1 = P, 3/1 = P + 2 G1, 5/1 = P + G1 + 2 G2, and 7/1 = 2 P + G1 + G2. | |||
Discard the last column to make a square matrix: | |||
||~ ||~ 2/1 ||~ 3/1 ||~ 5/1 || | |||
||~ period ||= 1 ||= 1 ||= 1 || | |||
||~ gen1 ||= 0 ||= 2 ||= 1 || | |||
||~ gen2 ||= 0 ||= 0 ||= 2 || | |||
Invert it. "/4" means that each entry is to be divided by the determinant of the last matrix, which is 4. | |||
||~ ||~ period ||~ gen1 ||~ gen2 ||~ || | |||
||~ 2/1 ||= 4 ||= -2 ||= -1 || || | |||
||~ 3/1 ||= 0 ||= 2 ||= -1 || || | |||
||~ 5/1 ||= 0 ||= 0 ||= 2 || /4 || | |||
Thus the period = (4, 0, 0)/4 = (1, 0, 0) = 2/1, gen1 = (-2, 2, 0)/4 = (-1, 1, 0)/2 = P5/2, and gen2 = (-1, -1, 2)/4 = [25/6]/4. | |||
Next, search for alternate generators... (to be continued) | |||
The primes can be octave-reduced, if preferred: | |||
||~ ||~ 2/1 ||~ 3/2 ||~ 5/4 ||~ 7/4 || | |||
||~ period = 2/1 ||= 1 ||= 0 ||= 0 ||= -1 || | |||
||~ gen1 = 3/2 ||= 0 ||= 1 ||= 0 ||= 2 || | |||
||~ gen2 = 5/4 ||= 0 ||= 0 ||= 1 ||= 2 ||</pre></div> | |||
<h4>Original HTML content:</h4> | <h4>Original HTML content:</h4> | ||
<div style="width:100%; max-height:400pt; overflow:auto; background-color:#f8f9fa; border: 1px solid #eaecf0; padding:0em"><pre style="margin:0px;border:none;background:none;word-wrap:break-word;width:200%;white-space: pre-wrap ! important" class="old-revision-html"><html><head><title>pergen names</title></head><body><strong>Pergen</strong> (pronounced &quot;peer-gen&quot;) sets are a way of identifying rank-2 and rank-3 regular temperaments by their periods and generators. They are somewhat JI-agnostic in that they don't use higher primes. Rank-2 names only use the first two primes in the prime subgroup, and rank-3 names only use the first three primes.<br /> | <div style="width:100%; max-height:400pt; overflow:auto; background-color:#f8f9fa; border: 1px solid #eaecf0; padding:0em"><pre style="margin:0px;border:none;background:none;word-wrap:break-word;width:200%;white-space: pre-wrap ! important" class="old-revision-html"><html><head><title>pergen names</title></head><body><strong>Pergen</strong> (pronounced &quot;peer-gen&quot;) sets are a way of identifying rank-2 and rank-3 regular temperaments by their periods and generators. They are somewhat JI-agnostic in that they don't use higher primes. Rank-2 names only use the first two primes in the prime subgroup, and rank-3 names only use the first three primes.<br /> | ||
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For non-standard prime groups, the period uses the first prime only, and the multi-gen uses the first two primes only. <a class="wiki_link" href="/Kite%27s%20color%20notation">Color notation </a>is used to indicate primes higher than 3. For example, 2.5.7 with 50/49 tempered out is {P8/2, y3} = half-octave, yellow-third.<br /> | For non-standard prime groups, the period uses the first prime only, and the multi-gen uses the first two primes only. <a class="wiki_link" href="/Kite%27s%20color%20notation">Color notation </a>is used to indicate primes higher than 3. For example, 2.5.7 with 50/49 tempered out is {P8/2, y3} = half-octave, yellow-third.<br /> | ||
<br /> | <br /> | ||
Rank-3 pergen | Rank-3 pergen sets have three intervals, any of which may be split. The unsplit 2.3.5... subgroup is {P8, P5, y3} = fifth-and-third-based. 2.3.5.7 with 50/49 tempered out is {P8/2, P5, y3}.<br /> | ||
<br /> | |||
Rank-4 temperaments have pergen sets of four intervals. Rank-1 temperaments could have pergen sets of one, such as {P8/12} for 12-edo or {P12/13} for 13-ed3, but there's no particular reason to do so.<br /> | |||
<br /> | |||
To find a temperament's pergen set, first find the PGM, the period generator mapping. This is a matrix with a column for each prime in the subgroup, and a row for each generator, counting the period as a special type of generator. Choose your generators so that all entries below the diagonal are zero. (This is not a problem with rank-2 temperaments.) You can use x31.com to find this matrix. Next make a square matrix by discarding columns for the higher primes. Then invert the matrix to get the monzos for each generator. Add/subtract periods from the generator to get alternate generators. Add/subtract both periods and generators from the 2nd generator to get more alternates. Choose the alternates to minimize the splitting and the cents.<br /> | |||
<br /> | |||
Example: 2.3.5.7 with 2401/2400 = (-5,-1,-2,4) tempered out. x31.com gives us this matrix:<br /> | |||
<table class="wiki_table"> | |||
<tr> | |||
<th><br /> | |||
</th> | |||
<th>2/1<br /> | |||
</th> | |||
<th>3/1<br /> | |||
</th> | |||
<th>5/1<br /> | |||
</th> | |||
<th>7/1<br /> | |||
</th> | |||
</tr> | |||
<tr> | |||
<th>period<br /> | |||
</th> | |||
<td style="text-align: center;">1<br /> | |||
</td> | |||
<td style="text-align: center;">1<br /> | |||
</td> | |||
<td style="text-align: center;">1<br /> | |||
</td> | |||
<td style="text-align: center;">2<br /> | |||
</td> | |||
</tr> | |||
<tr> | |||
<th>gen1<br /> | |||
</th> | |||
<td style="text-align: center;">0<br /> | |||
</td> | |||
<td style="text-align: center;">2<br /> | |||
</td> | |||
<td style="text-align: center;">1<br /> | |||
</td> | |||
<td style="text-align: center;">1<br /> | |||
</td> | |||
</tr> | |||
<tr> | |||
<th>gen2<br /> | |||
</th> | |||
<td style="text-align: center;">0<br /> | |||
</td> | |||
<td style="text-align: center;">0<br /> | |||
</td> | |||
<td style="text-align: center;">2<br /> | |||
</td> | |||
<td style="text-align: center;">1<br /> | |||
</td> | |||
</tr> | |||
</table> | |||
Thus 2/1 = P, 3/1 = P + 2 G1, 5/1 = P + G1 + 2 G2, and 7/1 = 2 P + G1 + G2.<br /> | |||
<br /> | |||
Discard the last column to make a square matrix:<br /> | |||
<table class="wiki_table"> | |||
<tr> | |||
<th><br /> | |||
</th> | |||
<th>2/1<br /> | |||
</th> | |||
<th>3/1<br /> | |||
</th> | |||
<th>5/1<br /> | |||
</th> | |||
</tr> | |||
<tr> | |||
<th>period<br /> | |||
</th> | |||
<td style="text-align: center;">1<br /> | |||
</td> | |||
<td style="text-align: center;">1<br /> | |||
</td> | |||
<td style="text-align: center;">1<br /> | |||
</td> | |||
</tr> | |||
<tr> | |||
<th>gen1<br /> | |||
</th> | |||
<td style="text-align: center;">0<br /> | |||
</td> | |||
<td style="text-align: center;">2<br /> | |||
</td> | |||
<td style="text-align: center;">1<br /> | |||
</td> | |||
</tr> | |||
<tr> | |||
<th>gen2<br /> | |||
</th> | |||
<td style="text-align: center;">0<br /> | |||
</td> | |||
<td style="text-align: center;">0<br /> | |||
</td> | |||
<td style="text-align: center;">2<br /> | |||
</td> | |||
</tr> | |||
</table> | |||
Invert it. &quot;/4&quot; means that each entry is to be divided by the determinant of the last matrix, which is 4.<br /> | |||
<table class="wiki_table"> | |||
<tr> | |||
<th><br /> | |||
</th> | |||
<th>period<br /> | |||
</th> | |||
<th>gen1<br /> | |||
</th> | |||
<th>gen2<br /> | |||
</th> | |||
<th><br /> | |||
</th> | |||
</tr> | |||
<tr> | |||
<th>2/1<br /> | |||
</th> | |||
<td style="text-align: center;">4<br /> | |||
</td> | |||
<td style="text-align: center;">-2<br /> | |||
</td> | |||
<td style="text-align: center;">-1<br /> | |||
</td> | |||
<td><br /> | |||
</td> | |||
</tr> | |||
<tr> | |||
<th>3/1<br /> | |||
</th> | |||
<td style="text-align: center;">0<br /> | |||
</td> | |||
<td style="text-align: center;">2<br /> | |||
</td> | |||
<td style="text-align: center;">-1<br /> | |||
</td> | |||
<td><br /> | |||
</td> | |||
</tr> | |||
<tr> | |||
<th>5/1<br /> | |||
</th> | |||
<td style="text-align: center;">0<br /> | |||
</td> | |||
<td style="text-align: center;">0<br /> | |||
</td> | |||
<td style="text-align: center;">2<br /> | |||
</td> | |||
<td>/4<br /> | |||
</td> | |||
</tr> | |||
</table> | |||
Thus the period = (4, 0, 0)/4 = (1, 0, 0) = 2/1, gen1 = (-2, 2, 0)/4 = (-1, 1, 0)/2 = P5/2, and gen2 = (-1, -1, 2)/4 = [25/6]/4.<br /> | |||
<br /> | |||
Next, search for alternate generators... (to be continued)<br /> | |||
<br /> | <br /> | ||
<br /> | |||
<br /> | |||
The primes can be octave-reduced, if preferred:<br /> | |||
<table class="wiki_table"> | |||
<tr> | |||
<th><br /> | |||
</th> | |||
<th>2/1<br /> | |||
</th> | |||
<th>3/2<br /> | |||
</th> | |||
<th>5/4<br /> | |||
</th> | |||
<th>7/4<br /> | |||
</th> | |||
</tr> | |||
<tr> | |||
<th>period = 2/1<br /> | |||
</th> | |||
<td style="text-align: center;">1<br /> | |||
</td> | |||
<td style="text-align: center;">0<br /> | |||
</td> | |||
<td style="text-align: center;">0<br /> | |||
</td> | |||
<td style="text-align: center;">-1<br /> | |||
</td> | |||
</tr> | |||
<tr> | |||
<th>gen1 = 3/2<br /> | |||
</th> | |||
<td style="text-align: center;">0<br /> | |||
</td> | |||
<td style="text-align: center;">1<br /> | |||
</td> | |||
<td style="text-align: center;">0<br /> | |||
</td> | |||
<td style="text-align: center;">2<br /> | |||
</td> | |||
</tr> | |||
<tr> | |||
<th>gen2 = 5/4<br /> | |||
</th> | |||
<td style="text-align: center;">0<br /> | |||
</td> | |||
<td style="text-align: center;">0<br /> | |||
</td> | |||
<td style="text-align: center;">1<br /> | |||
</td> | |||
<td style="text-align: center;">2<br /> | |||
</td> | |||
</tr> | |||
</table> | |||
</body></html></pre></div> |