Skip fretting system 90 5 17

One can play in 90-edo on an 18-edo guitar, by tuning the strings 17\90 (226 and 2/3 cents) apart. The resulting system allows a player to reach any 13-limit interval by crossing a maximum of only 4 frets. Octaves lie across six open strings and one fret, or on the same string 18 frets up (because 90 is divisible by 18).

The primes intervals lie in the following places:

note	fretboard position
0 steps = 1 % 1	string 0 fret 0
90 steps = 2 % 1	string 5 fret 1
53 steps = 3 % 2	string 4 fret - 3
29 steps = 5 % 4	string 2 fret - 1
73 steps = 7 % 4	string 4 fret 1
41 steps = 11 % 8	string 3 fret - 2
63 steps = 13 % 8	string 4 fret - 1
8 steps = 17 % 16	string - 1 fret 5
22 steps = 19 % 16	string 1 fret 1
47 steps = 23 % 16	string 1 fret 6
77 steps = 29 % 16	string 1 fret 12
86 steps = 31 % 16	string 3 fret 7

From these, the location of any compound interval can be added by vector-summing the string-fret positions of the interval's factors. See Skip fretting system 48 2 13 for details on how that's done.