729/704
| Interval information |
Alpharabian infra-apotomic quartertone,
undecimal major diesis
(Shannon, [math]\displaystyle{ \sqrt{nd} }[/math])
729/704, conventionally named the undecimal major diesis[1], is a medium comma measuring about 60.4 ¢. In Alpharabian tuning, it is called the Alpharabian infra-augmented prime or Alpharabian infra-apotomic quartertone.
It is a type of quartertone that differs from 33/32 by 243/242, and is itself the interval left over after subtracting 33/32 from 2187/2048. 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. This interval differs from the simpler 28/27 by the symbiotic comma. Furthermore, three instances of this interval fall short of 10/9 by a comma that is only a little over a cent in size.
Sagittal notation
In the Sagittal system, the downward version of this comma (possibly tempered) is represented by the sagittal and is called the 11 large diesis, or 11L for short, because the simplest interval it notates is 11/1 (equiv. 11/8), as for example in F-B . The upward version is called 1/11L or 11L up and is represented by .