Microtonal accidentals

[Hans Aberg]

FYI, some "Extended Helmholtz-Ellis JI” accidentals [1-2], in fact designed 
quite recently, but a nice input. There is also a Unicode font at [3]. Notation 
also mentioned at [4].

The arrow accidentals that LilyPond has, are used for syntonic comma 81/81 
alterations (staff system in Pythagorean tuning). LilyPond does not have those 
for double sharps and double flats. In addition, there are accidentals with 
double arrows, for double syntonic comma alterations, which LilyPond does not 
have. (And even triple arrows.)

Some traditional quartertone accidentals end up on the 11-limit rational 
interval 33/32, which seems to be a good idea: in E72, it is approximated with 
E24 quartertones.

1. http://www.newmusicbox.org/assets/72/HelmholtzEllisLegend.pdf
2. http://www.marcsabat.com/pdfs/notation.pdf
3. http://www.marcsabat.com/
4. https://en.wikipedia.org/wiki/Just_intonation