Kite's thoughts on pergens: Difference between revisions
Wikispaces>TallKite **Imported revision 627923165 - Original comment: ** |
Wikispaces>TallKite **Imported revision 627927613 - 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>2018-03-22 | : This revision was by author [[User:TallKite|TallKite]] and made on <tt>2018-03-22 23:51:59 UTC</tt>.<br> | ||
: The original revision id was <tt> | : The original revision id was <tt>627927613</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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or (22,-5,0,-5) ||= (P8/5, P5) ||= fifth-8ve ||= E = v<span style="vertical-align: super;">5</span>m2 ||= C D^^ Fv G^ Bbvv C ||= C G D A E... ||= a valid notation || | or (22,-5,0,-5) ||= (P8/5, P5) ||= fifth-8ve ||= E = v<span style="vertical-align: super;">5</span>m2 ||= C D^^ Fv G^ Bbvv C ||= C G D A E... ||= a valid notation || | ||
||= Blackwood ||= 256/243 ||= (P8/5, ^1) ||= rank-2 5-edo ||= E = m2 ||= C D=Eb E=F G A=Bb B=C ||= C Ev G#vv... ||= a valid notation || | ||= Blackwood ||= 256/243 ||= (P8/5, ^1) ||= rank-2 5-edo ||= E = m2 ||= C D=Eb E=F G A=Bb B=C ||= C Ev G#vv... ||= a valid notation || | ||
||= " ||= " ||= (P8/5, M3) ||= fifth-8ve major 3rd ||= E = v<span style="vertical-align: super;">5</span>m2 ||= C D^^ Fv G^ Bbvv C ||= C E G#... ||= invalid, no G, | ||= " ||= " ||= (P8/5, M3) ||= fifth-8ve major 3rd ||= E = v<span style="vertical-align: super;">5</span>m2 ||= C D^^ Fv G^ Bbvv C ||= C E G#... ||= invalid, no G, | ||
D or A notes || | D or A notes || | ||
== == | == == | ||
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For example, for 7-edo and 17-edo, the edomappings are (7, 4, 2) and (17, 10, 5). Their cross product is (0, -1, 2). This comma equates two generators with a 5th. The pergen is obviously (P8, P5/2). | For example, for 7-edo and 17-edo, the edomappings are (7, 4, 2) and (17, 10, 5). Their cross product is (0, -1, 2). This comma equates two generators with a 5th. The pergen is obviously (P8, P5/2). | ||
To verify the validity of this approach, one can find a specific JI ratio that maps to both 2\7 and 5\17 and use it to construct a comma. The ratio must contain only one higher prime, and must have color depth 1. If desired, a ratio of the form p/t can always be found, where p is a higher prime and t is a power of two. Any ratio between 3\14 and 5\14 maps to 2\7, and any ratio between 9\34 and 11\34 maps to 5\17. (The formula is (2n±1)/2d.) This gives us the ranges 257-429¢ and 318-388¢. Thus 5/4 barely works. The comma is (0, -1, 2) dot (2/1, 3/2, 5/4) = 25/24 = 71¢. A smaller comma can be found with a ratio more in the center of the range, such as 11/9, which yeilds 242/243. Because the direction of the cross product vector depends on the order of the two vectors multiplied, the sign of the comma is arbitrary, and the comma may be a descending ratio. If that happens, invert the comma to make 243/242. | To verify the validity of this approach, one can find a specific JI ratio that maps to both 2\7 and 5\17 and use it to construct a comma. The ratio must contain only one higher prime, and must have color depth 1. If desired, a ratio of the form p/t can always be found, where p is a higher prime and t is a power of two. Any ratio between 3\14 and 5\14 maps to 2\7, and any ratio between 9\34 and 11\34 maps to 5\17. (The formula is (2n±1)/2d.) This gives us the ranges 257-429¢ and 318-388¢. Thus 5/4 barely works. The comma is (0, -1, 2) dot (2/1, 3/2, 5/4) = 25/24 = 71¢. A smaller comma can be found with a ratio more in the center of the range, such as 11/9, which yeilds 242/243. Because the direction of the cross product vector depends on the order of the two vectors multiplied, the sign of the comma is arbitrary, and the comma may be a descending ratio. If that happens, invert the comma to make 243/242. | ||
Using unreduced edomappings gives the same result. If the basis is (2/1, 3/1, 5/1), we have (7, 11, 16) x (17, 27, 39) = (-3, -1, 2) = 25/24. If the basis is (2/1, 3/1, 11/9)... | Using unreduced edomappings gives the same result. If the basis is (2/1, 3/1, 5/1), we have (7, 11, 16) x (17, 27, 39) = (-3, -1, 2) = 25/24. If the basis is (2/1, 3/1, 11/9)... | ||
If the octave is split, | If the octave is split, | ||
||~ ||~ 12edo ||~ 13edo ||~ 14edo ||~ 15edo ||~ 16edo ||~ 17edo ||~ 18edo ||~ 19edo ||~ ||~ ||~ || | |||
||~ 12edo ||= -- ||= (P8, P5/7) ||= (P8/2, P5) ||= (P8/3, P5) ||= ||= ||= ||= ||= ||= ||= || | |||
||~ 13edo ||= ||= ||= ||= ||= ||= ||= ||= ||= ||= ||= || | |||
||~ 14edo ||= ||= ||= ||= ||= ||= ||= ||= ||= ||= ||= || | |||
||~ 15edo ||= ||= ||= ||= ||= ||= ||= ||= ||= ||= ||= || | |||
||~ 16edo ||= ||= ||= ||= ||= ||= ||= ||= ||= ||= ||= || | |||
||~ 17edo ||= ||= ||= ||= ||= ||= ||= ||= ||= ||= ||= || | |||
||~ 18edo ||= ||= ||= ||= ||= ||= ||= ||= ||= ||= ||= || | |||
||~ 19edo ||= ||= ||= ||= ||= ||= ||= ||= ||= ||= ||= || | |||
||~ ||= ||= ||= ||= ||= ||= ||= ||= ||= ||= ||= || | |||
||~ ||= ||= ||= ||= ||= ||= ||= ||= ||= ||= ||= || | |||
||~ ||= ||= ||= ||= ||= ||= ||= ||= ||= ||= ||= || | |||
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http://www.tallkite.com/misc_files/alt-pergenLister.zip | http://www.tallkite.com/misc_files/alt-pergenLister.zip | ||
The first section (PERGEN and Per/Gen cents) describes each pergen without regard to notational issues. The period and generator's cents are given, assuming a 5th of 700¢ + c. The generator is reduced, e.g. (P8/2, P5) has a generator of 100¢ + c, not 700¢ + c. The next two sections show a possible notation for P and G. The last section shows the unreduced pergen, and for false doubles, a possible single-pair notation. Red indicates problems. Generators of 50¢ or less are in red. Enharmonics of a 3rd or more are in red. | The first section (PERGEN and Per/Gen cents) describes each pergen without regard to notational issues. The period and generator's cents are given, assuming a 5th of 700¢ + c. The generator is reduced, e.g. (P8/2, P5) has a generator of 100¢ + c, not 700¢ + c. The next two sections show a possible notation for P and G. The last section shows the unreduced pergen, and for false doubles, a possible single-pair notation. Red indicates problems. Generators of 50¢ or less are in red. Enharmonics of a 3rd or more are in red. | ||
Screenshots of the first 38 pergens: | Screenshots of the first 38 pergens: | ||
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<td style="text-align: center;">C E G#...<br /> | <td style="text-align: center;">C E G#...<br /> | ||
</td> | </td> | ||
<td style="text-align: center;">invalid, no G, <br /> | <td style="text-align: center;">invalid, no G,<br /> | ||
D or A notes<br /> | D or A notes<br /> | ||
</td> | </td> | ||
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For example, for 7-edo and 17-edo, the edomappings are (7, 4, 2) and (17, 10, 5). Their cross product is (0, -1, 2). This comma equates two generators with a 5th. The pergen is obviously (P8, P5/2).<br /> | For example, for 7-edo and 17-edo, the edomappings are (7, 4, 2) and (17, 10, 5). Their cross product is (0, -1, 2). This comma equates two generators with a 5th. The pergen is obviously (P8, P5/2).<br /> | ||
<br /> | <br /> | ||
To verify the validity of this approach, one can find a specific JI ratio that maps to both 2\7 and 5\17 and use it to construct a comma. The ratio must contain only one higher prime, and must have color depth 1. If desired, a ratio of the form p/t can always be found, where p is a higher prime and t is a power of two. Any ratio between 3\14 and 5\14 maps to 2\7, and any ratio between 9\34 and 11\34 maps to 5\17. (The formula is (2n±1)/2d.) This gives us the ranges 257-429¢ and 318-388¢. Thus 5/4 barely works. The comma is (0, -1, 2) dot (2/1, 3/2, 5/4) = 25/24 = 71¢. A smaller comma can be found with a ratio more in the center of the range, such as 11/9, which yeilds 242/243. Because the direction of the cross product vector depends on the order of the two vectors multiplied, the sign of the comma is arbitrary, and the comma may be a descending ratio. If that happens, invert the comma to make 243/242. <br /> | To verify the validity of this approach, one can find a specific JI ratio that maps to both 2\7 and 5\17 and use it to construct a comma. The ratio must contain only one higher prime, and must have color depth 1. If desired, a ratio of the form p/t can always be found, where p is a higher prime and t is a power of two. Any ratio between 3\14 and 5\14 maps to 2\7, and any ratio between 9\34 and 11\34 maps to 5\17. (The formula is (2n±1)/2d.) This gives us the ranges 257-429¢ and 318-388¢. Thus 5/4 barely works. The comma is (0, -1, 2) dot (2/1, 3/2, 5/4) = 25/24 = 71¢. A smaller comma can be found with a ratio more in the center of the range, such as 11/9, which yeilds 242/243. Because the direction of the cross product vector depends on the order of the two vectors multiplied, the sign of the comma is arbitrary, and the comma may be a descending ratio. If that happens, invert the comma to make 243/242.<br /> | ||
<br /> | <br /> | ||
Using unreduced edomappings gives the same result. If the basis is (2/1, 3/1, 5/1), we have (7, 11, 16) x (17, 27, 39) = (-3, -1, 2) = 25/24. If the basis is (2/1, 3/1, 11/9)...<br /> | Using unreduced edomappings gives the same result. If the basis is (2/1, 3/1, 5/1), we have (7, 11, 16) x (17, 27, 39) = (-3, -1, 2) = 25/24. If the basis is (2/1, 3/1, 11/9)...<br /> | ||
<br /> | <br /> | ||
If the octave is split,<br /> | If the octave is split,<br /> | ||
<br /> | |||
<table class="wiki_table"> | |||
<tr> | |||
<th><br /> | |||
</th> | |||
<th>12edo<br /> | |||
</th> | |||
<th>13edo<br /> | |||
</th> | |||
<th>14edo<br /> | |||
</th> | |||
<th>15edo<br /> | |||
</th> | |||
<th>16edo<br /> | |||
</th> | |||
<th>17edo<br /> | |||
</th> | |||
<th>18edo<br /> | |||
</th> | |||
<th>19edo<br /> | |||
</th> | |||
<th><br /> | |||
</th> | |||
<th><br /> | |||
</th> | |||
<th><br /> | |||
</th> | |||
</tr> | |||
<tr> | |||
<th>12edo<br /> | |||
</th> | |||
<td style="text-align: center;">--<br /> | |||
</td> | |||
<td style="text-align: center;">(P8, P5/7)<br /> | |||
</td> | |||
<td style="text-align: center;">(P8/2, P5)<br /> | |||
</td> | |||
<td style="text-align: center;">(P8/3, P5)<br /> | |||
</td> | |||
<td style="text-align: center;"><br /> | |||
</td> | |||
<td style="text-align: center;"><br /> | |||
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<td style="text-align: center;"><br /> | |||
</td> | |||
</tr> | |||
<tr> | |||
<th>13edo<br /> | |||
</th> | |||
<td style="text-align: center;"><br /> | |||
</td> | |||
<td style="text-align: center;"><br /> | |||
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<tr> | |||
<th>14edo<br /> | |||
</th> | |||
<td style="text-align: center;"><br /> | |||
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<tr> | |||
<th>15edo<br /> | |||
</th> | |||
<td style="text-align: center;"><br /> | |||
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<td style="text-align: center;"><br /> | |||
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</tr> | |||
<tr> | |||
<th>16edo<br /> | |||
</th> | |||
<td style="text-align: center;"><br /> | |||
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</td> | |||
</tr> | |||
<tr> | |||
<th>17edo<br /> | |||
</th> | |||
<td style="text-align: center;"><br /> | |||
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<th>18edo<br /> | |||
</th> | |||
<td style="text-align: center;"><br /> | |||
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<th>19edo<br /> | |||
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make a glossary of all bolded terms?<br /> | make a glossary of all bolded terms?<br /> | ||
link from: ups and downs page, Kite Giedraitis page, MOS scale names page,<br /> | link from: ups and downs page, Kite Giedraitis page, MOS scale names page,<br /> | ||
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This PDF is a rank-2 notation guide that shows the full lattice for the first 15 pergens, up through the third-splits block. It includes alternate enharmonics for many pergens.<br /> | This PDF is a rank-2 notation guide that shows the full lattice for the first 15 pergens, up through the third-splits block. It includes alternate enharmonics for many pergens.<br /> | ||
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Alt-pergenLister lists out thousands of pergens, and suggests periods, generators and enharmonics for each one. Alternate enharmonics are not listed, but single-pair notation for false-double pergens is. It can also list only those pergens supported by a specific edo. Written in Jesusonic, runs inside Reaper.<br /> | Alt-pergenLister lists out thousands of pergens, and suggests periods, generators and enharmonics for each one. Alternate enharmonics are not listed, but single-pair notation for false-double pergens is. It can also list only those pergens supported by a specific edo. Written in Jesusonic, runs inside Reaper.<br /> | ||
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The first section (PERGEN and Per/Gen cents) describes each pergen without regard to notational issues. The period and generator's cents are given, assuming a 5th of 700¢ + c. The generator is reduced, e.g. (P8/2, P5) has a generator of 100¢ + c, not 700¢ + c. The next two sections show a possible notation for P and G. The last section shows the unreduced pergen, and for false doubles, a possible single-pair notation. Red indicates problems. Generators of 50¢ or less are in red. Enharmonics of a 3rd or more are in red. <br /> | The first section (PERGEN and Per/Gen cents) describes each pergen without regard to notational issues. The period and generator's cents are given, assuming a 5th of 700¢ + c. The generator is reduced, e.g. (P8/2, P5) has a generator of 100¢ + c, not 700¢ + c. The next two sections show a possible notation for P and G. The last section shows the unreduced pergen, and for false doubles, a possible single-pair notation. Red indicates problems. Generators of 50¢ or less are in red. Enharmonics of a 3rd or more are in red.<br /> | ||
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Screenshots of the first 38 pergens:<br /> | Screenshots of the first 38 pergens:<br /> | ||
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Listing all valid pergens is not a trivial task, like listing all valid edos or all valid MOS scales. Not all combinations of octave fractions and multigen fractions make a valid pergen. The search for rank-2 pergens can be done by looping through all possible square mappings [(x, y), (0, z)], and using the formula (P8/x, (i·z - y, x) / xz). While x is always positive and z is always nonzero, y can take on any value. For any x and z, y can be constrained to produce a reasonable cents value for 3/1. Let T be the tempered twefth 3/1. The mapping says T = y·P + z·G = y·P8/x + z·G. Thus y = x·(T/P8 - z·G/P8). We adopt the convention that G is less than half an octave. We constrain T so that the 5th is between 600¢ and 800¢, which certainly includes anything that sounds like a 5th. Thus T is between 3/2 and 5/3 of an octave. We assume that if the octave is stretched, the ranges of T and G will be stretched along with it. The outer ranges of y can now be computed, using the floor function to round down to the nearest integer, and the ceiling function to round up:<br /> | Listing all valid pergens is not a trivial task, like listing all valid edos or all valid MOS scales. Not all combinations of octave fractions and multigen fractions make a valid pergen. The search for rank-2 pergens can be done by looping through all possible square mappings [(x, y), (0, z)], and using the formula (P8/x, (i·z - y, x) / xz). While x is always positive and z is always nonzero, y can take on any value. For any x and z, y can be constrained to produce a reasonable cents value for 3/1. Let T be the tempered twefth 3/1. The mapping says T = y·P + z·G = y·P8/x + z·G. Thus y = x·(T/P8 - z·G/P8). We adopt the convention that G is less than half an octave. We constrain T so that the 5th is between 600¢ and 800¢, which certainly includes anything that sounds like a 5th. Thus T is between 3/2 and 5/3 of an octave. We assume that if the octave is stretched, the ranges of T and G will be stretched along with it. The outer ranges of y can now be computed, using the floor function to round down to the nearest integer, and the ceiling function to round up:<br /> |