5-7-9-15 by 9/8 bihexany

A 15-odd-limit Bihexany. This creates a scale of 1 81/80 15/14 243/224 9/8 135/112 9/7 81/56 3/2 27/16 9/5 27/14 2/1, with steps of 81/80 200/189 81/80 28/27 15/14 16/15 9/8 28/27 9/8 16/15 15/14 28/27. Since the base hexany has two perfect fifths, this is the obvious way to increase that to six, which also happens to give you an extra one that is flat by a marvel comma as a bonus. However, it results in a very uneven scale, with multiple 81/80's and other small intervals clustered around the root note with wide gaps on the opposite side, which means that while it might be harmonically strong, there is definite room for improvement on a melodic level.

Circle diagram.

! 5-7-9-15_by_9/8_Bihexany.scl
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5 7 9 15 by 9/8 2-combination Bihexany
12
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21.506
119.442
140.949
204.910
323.352
435.084
638.994
701.955
905.865
1017.596
1137.039
1200