Planar temperaments -- 1728/1715

This comma is defined by the approximation (12/7)^3 ~ 5, and a good
choice of generators is 12/7 and 3/2. Using them, we find the
following notes near the unison:

7/4 -- 3/2 -- 9/7 -- 35/32 -- 15/8
| | | | |
7/6 -- 1 -- 12/7 -- 35/24 -- 5/4
| | | | |
14/9-- 4/3 -- 8/7 -- 35/18 -- 5/3

The least-squares seven limit values have a fifth which is 1.31 cents
flat and a major third 1.31 cents sharp, and a 7 twice as sharp at
2.61 cents.