Arcturus hendecatonic notation

Arcturus hendecatonic notation is a notation system for EDTs and no-twos music, developed by CompactStar. It is based on the 2L 9s⟨3/1⟩ MOS scale generated by approximately 5/3. The 5/3 generator connects this MOS to the 3.5 subgroup and (in the basic-hard range) Arcturus temperament, similar to how the diatonic scale is connected to the 3-limit and (in the soft-basic range) meantone temperament. The preferred generator is the patent val 5/3, unless it is extremely inaccurate (as is the case in some very small EDTs) and does not generate a 2L 9s⟨3/1⟩ scale. Most of the generators for larger EDTs are tunings for Arcturus temperament, but some fall sharp or flat analogous

The 9|1 mode of 2L 9s⟨3/1⟩ is represented by 11 naturals CDEFGHJKLAB, and #/b accidentals are used to raise and lower by a chroma (L - s). For relative notation, the TAMNAMS convention of zero-based indices is used. Assuming Arcturus temperament where 7/3 is mapped to the perfect 8-step, the chord 3:5:7 is notated as C - H - L (P0 - P5 - M8). To notate larger EDTs, Arcturus hendecatonic notation can be combined with ups and downs notation, with ^/v accidentals raising and lowering by 1 EDTstep.

Examples

9edt:

Steps	Absolute notation	Relative notation
0	C	perfect 0-step
1	D	perfect 1-step
2	E	perfect 2-step
3	E	major 2-step
4	F	major 3-step
5	G	major 4-step
6	H	perfect 5-step
7	J	perfect 6-step
8	Kb	minor 7-step
9	K	major 7-step
10	L	major 8-step
11	A	major 9-step
12	B	major 10-step
13	C	perfect 11-step

13edt (Bohlen-Pierce):

Steps	Absolute notation	Relative notation
0	C	perfect 0-step
1	Db	minor 1-step
2	D	major 1-step
3	E	major 2-step
4	F	major 3-step
5	G	major 4-step
6	H	perfect 5-step
7	J	perfect 6-step
8	Kb	minor 7-step
9	K	major 7-step
10	L	major 8-step
11	A	major 9-step
12	B	major 10-step
13	C	perfect 11-step