Fractional sharp notation

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

The letter notation is a notation scheme developed by CompactStar for just intonation up to the 31-limit and some regular temperaments. It is Pythagorean notation with the letters H-Z used as accidentals for commas in higher prime limits (starting from H to avoid conflict with note names, and skipping M to avoid conflict with the abbreviation for "major"). The rationale for using letters as accidentals is that they are ASCII-compatible, and easy to memorize if in alphabetical order.

Accidentals

Prime limit	Letter	Ratio	Letter	Ratio
5	H	81/80	I	80/81
7	J	64/63	K	63/64
11	L	33/32	N	32/33
13	O	1053/1024	P	1024/1053
17	Q	4131/4096	R	4096/4131
19	S	513/512	T	512/513
23	U	736/729	V	729/736
29	W	261/256	X	256/261
31	Y	32/31	Z	31/32

For example, 5/4 is IM3 (I-major third), 7/4 is Km7 (K-minor seventh) and 11/8 is LP4 (L-perfect fourth). Above C, these would be written IE, KBb and LF respectively.