harmonic seventh (7:4). There is also a smaller septimal chromatic semitone of 21:20 (play) between a septimal minor seventh and a fifth (21:8) and an octave
7-limit commas that 12-ET tempers out is the septimal kleisma, which is equal to 225/ 224 , or 32×52 /25×71. 12-ET's other 7-limit commas include:
near to 2⁄9-comma meantone the A4 is near to the ratio 7:5 (582.51) and the d5 to 10:7 (617.49), which is what these intervals are in septimal meantone temperament
called the syntonic comma. The septimalcomma, the ratio of 64:63, is a 7 limit interval which is the distance between the Pythagorean semi-ditone, 32 /