Fractional sharp notation

Revision as of 09:46, 1 March 2024 by CompactStar (talk | contribs)

VERY WIP (I'll move it to the main namespace if it's finished.)

The fractional sharp notation (FSN) is a notation developed by CompactStar that is largely an extension of circle-of-fifths notation, which can be used for EDOs, and secondarily for temperaments and just intonation subgroups of rank 3. It represents all intervals with conventional accidentals, but with sharps and flats extended to have an arbitrary rational amount, denoted by a superscript or caret (like #1/2 for half-sharp) except for in the case of single and double accidentals. This means that there is support for not only half-sharps and half-flats, but third-sharps, third-flats and so on, supporting almost all EDO systems. Multiples of 7edo up to 35edo, excluding 7edo itself, are not supported, but these are possible to be notated as subsets of larger EDOs. In particular, 14edo and 21edo can be notated as subsets of 42edo, 28edo as a subset of 56edo, and 35edo as a subset of 70edo or using the alternative fifth from 5edo. 1edo to 4edo are obviously notated as subsets, and 8edo is also required to be notated as a subset of 16edo, 24edo, or 32edo with no fifth except for 750 cents. Antidiatonic fifths may be notated using both the "major wider than minor" and "minor wider than major" systems, depending on what is needed.

The sharp and flat accidentals are always taken to raise and lower by an augmented union or apotome. In a given EDO system, the step size is 1 over the sharpness of a sharp. In interval naming, x-augmented and x-diminished raise and lower by x times a chromatic semitone. These are used in the same way as augmented and diminished normally are, but additionally, "augmented minor" and "diminished major" are used for constructions like "1/3-augmented minor 3rd", meaning a minor 3rd raised by 1/3 of an apotome (formerly these were described as a "fraction of major" like 1/3-major, the updated version was suggested by Frostburn). Since 1/2-augmented minor and 1/2-diminished major mean the same thing, they are replaced with the more conventional term "neutral".

Here is an example for 22edo:

Degree Cents Notation
0 0.000 perfect unison P1 D
1 54.545 minor 2nd m2 Eb
2 109.091 1/3-aug minor 2nd 1/3-AM2 Eb2/3
3 163.636 1/3-dim major 2nd 1/3-dM2 Eb1/3
4 218.182 major 2nd M2 E
5 272.727 minor 3rd m3 F
6 327.273 1/3-aug minor 3rd 1/3-Am3 F#1/3
7 381.818 1/3-aug dim 3rd 1/3-dM3 F#2/3
8 436.364 major 3rd M3 F#
9 490.909 perfect fourth P4 G
10 545.455 1/3-aug 4th, dim 5th 1/3-A4, d5 G#1/3, Ab
11 600.000 2/3-aug 4th, 2/3-dim 5th 2/3-A4, 2/3-d5 G#2/3, Ab2/3
12 654.545 aug 4th, 1/3-dim 5th A4, 1/3-d5 G#, Ab1/3
13 709.091 perfect 5th P5 A
14 763.636 minor 6th m6 Bb
15 818.182 1/3-aug minor 6th 1/3-Am6 Bb2/3
16 872.727 1/3-dim major 6th 1/3-dM6 Bb1/3
17 927.273 major 6th M6 B
18 981.818 minor 7th m7 C
19 1036.364 1/3-aug minor 7th 1/3-Am7 C#1/3
20 1090.909 1/3-dim major 7th 1/3-dM7 C#2/3
21 1145.455 major 7th M7 C#
22 1200.000 perfect octave P8 D

Just intonation

This segment will probably removed or changed

Accidentals

Prime limit Comma Sharps
5 81/80 1/5
7 64/63 1/4
11 33/32 1/2
13 1053/1024 1/2
17 4131/4096 1/8
19 513/512 1/34
23 736/729 1/7