256/255: Difference between revisions

| Name = septendecimal kleisma, <br>charisma, char comma, <br>octave-reduced 255th subharmonic

| Color name = 17ug1, sugu 1sn, <br>Sugu comma

{{Redirect-distinguish|Charisma|Horcrux}}

'''256/255''', the '''septendecimal kleisma''', '''charisma''', '''char comma''' or '''octave-reduced 255th subharmonic''' is a [[small comma|small]] [[17-limit]] [[superparticular]] comma about 6.8 [[cent]]s in size. It is the difference between [[16/15]] (the classical diatonic semitone) and [[17/16]] (the large septendecimal semitone) and forms the amount by which a stack consisting of [[15/8]] and 17/16 falls short of an [[octave]].

By tempering it out is defined the full 17-limit rank-6 '''charismic temperament''' or 2.3.5.17 subgroup rank-3 '''charic temperament''', which enables the [[charismic chords]].

: sval mapping generators: ~2, ~3, ~5

[[Optimal tuning]] ([[CTE]]): ~2 = 1\1, 3/2 = 702.6467, 5/4 = 387.7981

[[Mapping]]: <br>

[[Optimal tuning]] ([[CTE]]): ~2 = 1\1, 3/2 = 702.6467, 5/4 = 387.7981, ~7/4, ~11/8, ~13/8

Before 2023, this interval was known as ''septendecimal kleisma'' or ''255th subharmonic''.

The "char" in the name ''charisma'' (or ''char comma'') refers to the char data type in C-derived programming languages, where the char represents a byte of at least or exactly 8 bits. Thereby, the maximum unsigned value for an 8-bit char is 255 and the number of values an 8-bit char can take is 256, hence 256/255.

The former name ''diasemisma'' was proposed by [[User:Xenllium|Xenllium]] in May 2023. It is a contraction of ''diatonic semitone'' into a single word. In some contexts, both [[16/15]] and [[17/16]] are considered minor second (ie. [[diatonic semitone]]), namely classical diatonic semitone and minor diatonic semitone respectively. However, a rename to ''charisma'' was proposed as part of an effort to make naming more standardised and for a number of reasons including potential confusion with [[diasem]] and the former nonconforming naming of [[horcrux]] in the 11- and 13-limit (which were formerly named "charisma" and "charismic", creating a potential false impression that the former was a comma, not a temperament, and that the latter was the temperament defined by tempering that comma in the corresponding prime limit); specifically, see the [[Talk:256/255|talk page]] and [[Temperament naming #Contemporary rules]] for details.

The rename took place as Starshine (from the [[XA Discord]] server) suggested (half-jokingly) that a chance had been missed to name it the ''charisma'' in December 2023, a name which [[User:Godtone|Godtone]] took favor to and championed which then caused awareness of nonconforming names of two [[horcrux]] temeraments. A revision to ''charsma'' (no-''i'' spelling) was proposed by Xenllium in January 2024 for disambiguation but this would cause inconsistency with the -ic/-ismic/-isma rule which is a reason that those same temperaments were already being proposed to be renamed.