! mersen-ban.scl ! For keyboard designs of Mersenne (1635) & Ban (1639), 10 black and extra D. Traité, p. 44-45 18 ! 25/24 16/15 10/9 9/8 75/64 6/5 5/4 4/3 25/18 45/32 3/2 25/16 8/5 5/3 16/9 9/5 15/8 2/1