33/32: Difference between revisions

| Sound = jid_33_32_pluck_adu_dr220.mp3

| Comma = yes

 

'''33/32''', the '''al-Farabi quarter tone'''<ref group="note">The name goes back to Abu Nasr Al-Farabi (in Western reception also Alpharabius), see [[Wikipedia: Al-Farabi]].</ref>, '''undecimal quarter tone''', or '''undecimal formal comma''', is a [[superparticular]] [[ratio]] which differs by a [[385/384|keenanisma (385/384)]], from the [[36/35|septimal quarter tone (36/35)]]. Raising a just [[4/3|perfect fourth (4/3)]] by the al-Farabi quarter-tone leads to the [[11/8|undecimal superfourth (11/8)]]. Raising it instead by 36/35 leads to the [[48/35|septimal superfourth (48/35)]] which approximates 11/8. Apart from this, it is also the interval between [[32/27]] and [[11/9]], and between [[9/8]] and [[12/11]].

 

Because of its close proximity to [[28/27]], from which it differs only by [[Pentacircle comma|896/891]], one could reasonably argue that 33/32 is the [[undecimal]] counterpart to 28/27 in a way, particularly if treated as an interval in its own right.  However, despite this, 33/32 generally has properties more akin to a chromatic interval than to anything resembling a diatonic interval.  In addition, 33/32 could arguably have been used as a melodic interval in the Greek Enharmonic Genus, and if so, there are several possibilities for the resulting [[tetrachord]]. The most obvious of these possibilities would be to include 32:33:34 within the interval of a perfect fourth, in which case this [[ancient Greek]] scale can be approximated in [[22edo]] and [[24edo]], with the comma [[1089/1088]] being tempered out so that 33/32 and 34/33 are equated.  Another possibility, however, is that the semitone was [[16/15]], which, according to [[Wikipedia: Genus (music)|Wikipedia]], is indirectly attested to in the writings of [[Ptolemy]], and thus, if 33/32 was in fact used, it would have been paired with [[512/495]].

 

It should be noted that in some significant respects, treating 33/32 as a comma rather than as an important musical interval in its own right sells it short, and results in the failure to correctly define the properties of certain intervals. Namely, a stack of two 33/32 intervals equals [[1089/1024]], a type of chromatic semitone that has [[128/121]] as its diatonic counterpart.  Furthermore, 33/32 is one of two distinct 11-limit quartertone intervals required to add up to a whole tone, with [[4096/3993]] being the other&mdash;specifically, adding 4096/3993 to a stack of three 33/32 quartertones yields [[9/8]].  In addition to all this, 33/32 finds a special place in [[Alpharabian tuning]] and it is from this area of microtonal theory, among a select few others, that 33/32 acquires the names "'''Alpharabian parachroma'''" and "'''Alpharabian ultraprime'''", names that at this point are only used in said theoretical contexts. While many may be accustomed to thinking of 33/32 and [[729/704]] as "semiaugmented primes", this analysis is only completely accurate when [[243/242]] is tempered out.

 

If treated as a comma to be tempered out in the 2.3.11 [[subgroup]], it results in the [[no-fives subgroup temperaments #Io|io]] temperament, giving rise to the name '''io comma'''. The temperament is generated by a flat fifth ([[7edo]] and [[26edo]] being good tunings) which represents both [[3/2]] and [[16/11]].

 

[[22edo]] and [[23edo]]'s step sizes are good, albeit in[[consistent]] approximations of this interval. Since equal-step tuning of 33/32 is roughly equivalent to 22.5edo, 2 steps of [[45edo]] represent the interval with great accuracy. [[46edo]] inherits mapping from 23edo and does it consistently.

 

This interval is significant in [[Functional Just System]] and [[Helmholtz&ndash;Ellis notation]] as the undecimal formal comma which translates a Pythagorean interval to a nearby undecimal interval.

 

=== Ben Johnston's notation ===

In [[Ben Johnston's notation]], this interval is denoted with &uarr;, and its reciprocal as &darr;. If the base note is C, then 11/8 is represented by C&ndash;F&uarr;.  

 

In the [[Sagittal]] system, this comma (possibly tempered) is represented by the sagittal {{sagittal | /|\ }} and is called the '''11 medium diesis''', or '''11M''' for short, because the simplest interval it notates is 11/1 (equiv. 11/8), as for example in C–F{{nbhsp}}{{sagittal | /|\ }}. The downward version is called '''1/11M''' or '''11M down''' and is represented by {{sagittal| \!/ }}.

 

== See also ==

* [[1ed33/32]] &ndash; equal multiplication of this interval

* [[64/33]] &ndash; its [[octave complement]]

* [[16/11]] &ndash; its [[fifth complement]]

* [[32/31]] &ndash; the tricesimoprimal counterpart

* [[:File:Ji-33-32-csound-foscil-220hz.mp3]] &ndash; alternative sound example

 

<references group="note" />