2/7-comma meantone is the tuning of meantone temperament in which the just perfect fifth of 3/2 is flattened by 2/7 of a syntonic comma (81/80). It is one of the meantone tunings proposed early on, by Gioseffo Zarlino, Francisco Salinas and Vincenzo Galilei. It may be described as the regular tuning which tempers out 81/80 and tunes 2/1 and 25/24 purely. It is also the tuning where the major third (5/4) and the minor third (6/5) are equally flat from JI by 1/7 syntonic comma (c. 3.1 cents). It is approximated roughly by 50edo and 69edo sharply and flatly, respectively, and near perfectly by 119edo using the b val flat 5th.
Tuning map: ⟨1200 1895.8103 2783.2414 3358.1035]
Mistuning map: ⟨0 -6.1447 -3.0723 -10.7224]