128/99
| Interval information |
undecimal minor fourth,
Alpharabian paraminor fourth,
just paraminor fourth
reduced subharmonic
(Shannon, [math]\displaystyle{ \sqrt{nd} }[/math])
In 11-limit just intonation, 128/99 is an undecimal subfourth measuring about 444.8¢. It is the inversion of 99/64, the undecimal superfifth. This interval is also known as the undecimal minor fourth through analogy with 11/8 being the "major fourth" as named by Ivan Wyschnegradsky, and can additionally be somewhat similarly dubbed the Alpharabian paraminor fourth or even the just paraminor fourth. It is distinguished from the simpler 22/17 by the twosquare comma.
Despite being relatively more complex, 128/99 is actually pretty useful as an interval for those who work more extensively with the 11-limit. For example, Margo Schulter has stated that it is useful in a Neo-Medieval European setting as a substitute for 9/7, and is closer to the likeliest interpretation- such as that of Jay Rahn- of Marcheto (or Marchettus or Marchetto) of Padua in 1318 than her own older septimal interpretation of the same interval.
Approximation
This interval is especially close to the 10th step of 27edo.