Hemipyth: Difference between revisions
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A '''hemipyth''' (or '''"hemipythagorean"''') interval is an [[interval]] in the <math>\sqrt{2}\,.\sqrt{3}</math> [[subgroup]] i.e. intervals that can be constructed by multiplying half-integer powers of 2 and 3. | A '''hemipyth''' (or '''"hemipythagorean"''') interval is an [[interval]] in the <math>\sqrt{2}\,.\sqrt{3}</math> [[subgroup]] i.e. intervals that can be constructed by multiplying half-integer powers of 2 and 3. | ||
Notable hemipyth intervals include the neutral third <math>\sqrt{\frac{3}{2}} = \frac{\sqrt{3}}{\sqrt{2}}</math>, semioctave <math>\sqrt{2}</math>, and the semifourth <math>\sqrt{\frac{4}{3}} = \frac{2}{\sqrt{3}}</math>. | Notable hemipyth intervals include the neutral third <math>\sqrt{\frac{3}{2}} = \frac{\sqrt{3}}{\sqrt{2}}</math>, semioctave <math>\sqrt{2}</math>, and the semifourth <math>\sqrt{\frac{4}{3}} = \frac{2}{\sqrt{3}}</math>. | ||
Many temperaments naturally produce intervals that split ~3 | Many temperaments naturally produce intervals that split ~{{sfrac|3|2}}, ~2, or ~{{sfrac|4|3}} exactly in half and can thus be interpreted as neutral thirds, semioctaves, or semifourths within the temperament. | ||
== Equal temperaments == | == Equal temperaments == | ||
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* Either the edo is even and it features at least <math>\sqrt{2}</math> (which is tuned "pure" when the octave is tuned pure). | * Either the edo is even and it features at least <math>\sqrt{2}</math> (which is tuned "pure" when the octave is tuned pure). | ||
* Or one of the following is true: | * Or one of the following is true: | ||
** The closest approximation to 3 | ** The closest approximation to {{sfrac|3|2}} spans an even number of edosteps (leading to an approximation to <math>\sqrt{\frac{3}{2}}</math>) | ||
** The closest approximation to 4 | ** The closest approximation to {{sfrac|4|3}} spans an even number of edosteps (leading to an approximation to <math>\sqrt{\frac{4}{3}}</math>) | ||
{| class="wikitable" | {| class="wikitable" | ||
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== Notation == | == Notation == | ||
The Pythagorean (2.3) part of hemipyth can be notated using traditional notation where octaves represent multiples of 2 | The Pythagorean (2.3) part of hemipyth can be notated using traditional notation where octaves represent multiples of {{sfrac|2|1}}, chain of fifths denotes multiples of {{sfrac|3|2}}, the sharp sign is equal to {{sfrac|2187|2048}} etc. | ||
A prototypical 5L 2s 5|1 (Ionian) scale would be spelled C, D, E, F, G, A, B, (C). | A prototypical 5L 2s 5|1 (Ionian) scale would be spelled C, D, E, F, G, A, B, (C). | ||
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=== Semioctaves === | === Semioctaves === | ||
In traditional notation the octave spans 7 diasteps which means that it splits into two interordinal {{ | In traditional notation the octave spans 7 diasteps which means that it splits into two interordinal {{sfrac|3|1|2}} diasteps or two perfect 4.5ths ("four-and-a-halves") if we wish to remain backwards compatible with the 1-indexed traditional notation. | ||
Intervals retain their quality when the frequency ratio is multiplied by the perfect semioctave <math>\sqrt{2}</math>, e.g. {{nowrap|M6 − P4.5 {{=}} M2.5 {{=}} ({{frac|9|8}})<sup>3/2</sup>}}. | Intervals retain their quality when the frequency ratio is multiplied by the perfect semioctave <math>\sqrt{2}</math>, e.g. {{nowrap|M6 − P4.5 {{=}} M2.5 {{=}} ({{frac|9|8}})<sup>3/2</sup>}}. | ||
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=== Semifourths === | === Semifourths === | ||
Luckily we don't need to introduce any more generalizations to the notation to indicate <math>\sqrt{\frac{4}{3}}</math>. It's a neutral {{ | Luckily we don't need to introduce any more generalizations to the notation to indicate <math>\sqrt{\frac{4}{3}}</math>. It's a neutral {{sfrac|2|1|2}} or a α{{demiflat2}} (alp semiflat) w.r.t middle C. | ||
Nicknames are still assigned to make it easier to talk about the [[5L 4s]] scale generated by <math> | Nicknames are still assigned to make it easier to talk about the [[5L 4s]] scale generated by <math>\sim\vsp\sqrt{\frac{4}{3}}</math> against the octave. | ||
{| class="wikitable" | {| class="wikitable" | ||
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The neutral third receives only half of the tuning damage of the fifth so it has a strong character even if the fifth isn't tuned very pure. The irrational nature of <math>\sqrt{\frac{3}{2}}</math> also makes it more tolerant of imprecise tuning. | The neutral third receives only half of the tuning damage of the fifth so it has a strong character even if the fifth isn't tuned very pure. The irrational nature of <math>\sqrt{\frac{3}{2}}</math> also makes it more tolerant of imprecise tuning. | ||
The same goes for the semifourth. A poorly tuned ~4 | The same goes for the semifourth. A poorly tuned ~{{sfrac|4|3}} still results in a decent <math>\sim\vsp\sqrt{\frac{4}{3}}</math> (assuming it's featured in the tuning in the first place). | ||
=== Signposts === | === Signposts === | ||
Due to their low damage in supporting temperaments, the octave ({{ | Due to their low damage in supporting temperaments, the octave ({{sfrac|2|1}}), semioctave <math>\left(\sqrt{2}\right)</math>, perfect fifth ({{sfrac|3|2}}), perfect fourth ({{sfrac|4|3}}), neutral third <math>\left(\sqrt{\frac{3}{2}}\right)</math>, neutral sixth <math>\left(\sqrt{\frac{8}{3}}\right)</math>, semifourth <math>\left(\sqrt{\frac{4}{3}}\right)</math>, semitwelfth <math>\left(\sqrt{3}\right)</math>, "hemitone" <math>\left(\sqrt{\frac{9}{8}}\right)</math>, and "contrahemitone" <math>\left(\sqrt{\frac{32}{9}}\right)</math> all provide good signposts for navigating around otherwise unfamiliar scales. | ||
While untempered semitones usually come as unequal pairs consisting of an augmented unison and a minor second, the "hemitone" is always exactly the geometric half of a 9 | While untempered semitones usually come as unequal pairs consisting of an augmented unison and a minor second, the "hemitone" is always exactly the geometric half of a {{sfrac|9|8}} whole tone. The "contrahemitone" is its octave-complement. | ||
== Temperament interpretations == | == Temperament interpretations == | ||
Under [[ploidacot]] classification diploid temperaments feature <math> | Under [[ploidacot]] classification diploid temperaments feature <math>\sim\vsp\sqrt{2}</math>, dicot temperaments have <math>\sim\vsp\sqrt{\frac{3}{2}}</math> and alpha-dicot temperaments feature <math>\sim\vsp\sqrt{\frac{4}{3}}</math> (by virtue of having a <math>\sim\vsp\sqrt{3}</math>). | ||
Full hemipyth support is indicated by at least "diploid dicot". Examples include: | Full hemipyth support is indicated by at least "diploid dicot". Examples include: | ||
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|+ style="font-size: 105%;" | Higher-prime interpretations of hemipyth intervals | |+ style="font-size: 105%;" | Higher-prime interpretations of hemipyth intervals | ||
|- | |- | ||
! Temperament !! <math> | ! Temperament !! <math>\sim\vsp\sqrt{2}</math> !! <math>\sim\vsp\sqrt{\frac{3}{2}}</math> !! <math>\sim\vsp\sqrt{\frac{4}{3}}</math> !! contorted !! rank-2 | ||
|- | |- | ||
| [[decimal]] || ~7 | | [[decimal]] || ~{{sfrac|7|5}} || ~{{sfrac|5|4}} || ~{{sfrac|7|6}} || no || yes | ||
|- | |- | ||
| [[anguirus]] || ~45 | | [[anguirus]] || ~{{sfrac|45|32}} || ~{{sfrac|56|45}} || ~{{sfrac|7|6}} || no || yes | ||
|- | |- | ||
| [[sruti]] || ~45 | | [[sruti]] || ~{{sfrac|45|32}} || ~{{sfrac|175|144}} || ~{{sfrac|81|70}} || no || yes | ||
|- | |- | ||
| [[Subgroup temperaments#Pakkanian hemipyth|pakkanian hemipyth]] || ~17 | | [[Subgroup temperaments#Pakkanian hemipyth|pakkanian hemipyth]] || ~{{sfrac|17|12}} || ~{{sfrac|11|9}} || ~{{sfrac|15|13}} || no || yes | ||
|- | |- | ||
| [[harry]] || ~17 | | [[harry]] || ~{{sfrac|17|12}} || ~{{sfrac|11|9}} || ~{{sfrac|15|13}} || yes || yes | ||
|- | |- | ||
| [[semimiracle]] || ~91 | | [[semimiracle]] || ~{{sfrac|91|64}} || ~{{sfrac|11|9}} || ~{{sfrac|15|13}} || yes || yes | ||
|- | |- | ||
| [[hemidim]] || ~36 | | [[hemidim]] || ~{{sfrac|36|25}} || ~{{sfrac|25|21}} || ~{{sfrac|7|6}} || yes || yes | ||
|- | |- | ||
| [[greenland]] || ~99 | | [[greenland]] || ~{{sfrac|99|70}} || ~{{sfrac|49|40}} || ~{{sfrac|15|13}}~{{sfrac|231|200}} || no || no | ||
|- | |- | ||
| [[semisema]] || ~108 | | [[semisema]] || ~{{sfrac|108|77}} || ~{{sfrac|11|9}} || ~{{sfrac|7|6}} || no || yes | ||
|- | |- | ||
| [[quadritikleismic]] || ~625 | | [[quadritikleismic]] || ~{{sfrac|625|441}} || ~{{sfrac|49|40}} || ~{{sfrac|125|108}} || yes || yes | ||
|- | |- | ||
| [[decoid]] || ~99 | | [[decoid]] || ~{{sfrac|99|70}} || ~{{sfrac|49|40}} || ~{{sfrac|4725|4096}} || yes || yes | ||
|} | |} | ||
Above contorted tunings don't have a <math> | Above contorted tunings don't have a <math>\sim\vsp\sqrt{2}</math> period with a <math>\sim\vsp\sqrt{3}</math> generator, but introduce further splits. Higher than rank-2 temperaments introduce further structure that goes beyond basic hemipyth. | ||
Some possible interpretations for <math> | Some possible interpretations for <math>\sim\vsp\sqrt{2}</math> are: | ||
{| class="wikitable" | {| class="wikitable" | ||
|+ style="font-size: 105%;" | Higher-prime interpretations of <math>\sqrt{2}</math> | |+ style="font-size: 105%;" | Higher-prime interpretations of <math>\sqrt{2}</math> | ||
|- | |- | ||
! Temperament !! <math> | ! Temperament !! <math>\sim\vsp\sqrt{2}</math> !! contorted !! rank-2 | ||
|- | |- | ||
| [[jubilic]] || ~7 | | [[jubilic]] || ~{{sfrac|7|5}} || no || yes (2.5.7) | ||
|- | |- | ||
| [[diaschismic]] || ~45 | | [[diaschismic]] || ~{{sfrac|45|32}} || no || yes (2.3.5) | ||
|- | |- | ||
| [[semitonic]] || ~17 | | [[semitonic]] || ~{{sfrac|17|12}} || no || yes (2.3.17) | ||
|- | |- | ||
| [[kalismic temperaments|kalismic]] || ~99 | | [[kalismic temperaments|kalismic]] || ~{{sfrac|99|70}} || no || no | ||
|} | |} | ||
Some possible interpretations for <math> | Some possible interpretations for <math>\sim\vsp\sqrt{3}</math> are: | ||
{| class="wikitable" | {| class="wikitable" | ||
|+ style="font-size: 105%;" | Higher-prime interpretations of <math>\sqrt{3}</math> | |+ style="font-size: 105%;" | Higher-prime interpretations of <math>\sqrt{3}</math> | ||
|- | |- | ||
! Temperament !! <math> | ! Temperament !! <math>\sim\vsp\sqrt{3}</math> !! contorted !! rank-2 | ||
|- | |- | ||
| [[semaphore]] || ~7 | | [[semaphore]] || ~{{sfrac|7|4}} || no || yes (2.3.7) | ||
|- | |- | ||
| [[barbados]] || ~26 | | [[barbados]] || ~{{sfrac|26|15}} || no || yes (2.3.{{sfrac|13|5}}) | ||
|} | |} | ||
Some possible interpretations for | Some possible interpretations for <math>\sim\vsp\frac{3}{2}</math> are: | ||
{| class="wikitable" | {| class="wikitable" | ||
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! Temperament !! <math>\sqrt{~\frac{3}{2}}</math> !! contorted !! rank-2 | ! Temperament !! <math>\sqrt{~\frac{3}{2}}</math> !! contorted !! rank-2 | ||
|- | |- | ||
| [[dicot]] || ~5 | | [[dicot]] || ~{{sfrac|5|4}} || no || yes (2.3.5) | ||
|- | |- | ||
| [[Rastmic clan#Neutral|neutral]] || ~11 | | [[Rastmic clan#Neutral|neutral]] || ~{{sfrac|11|9}} || no || yes (2.3.11) | ||
|- | |- | ||
| [[jove]] || ~11 | | [[jove]] || ~{{sfrac|11|9}}~{{sfrac|49|40}} || no || no | ||
|} | |} | ||