EDO values other than 12-EDO and non-linear keys

[rpatters1]

In reviewing the example files, I realized that the current specification as documented assumes that

1. All key signatures are linear.
2. The only EDO (equal division of the octave) is 12-EDO.

Non linear keys are used in a number ethnic styles. I'm most familiar with Freyish in klezmer music, which has a flat 2, raised 3, flat 6. So the key signature for D-Freyish has F#, Eb, and Bb. I am not sure how this might be worked into the current framework, but I think it should be.

Support for microtonal scales I think could be added quite easily. The global measures object could add an edo object:

"global": {
      "measures": [
         {
            "edo": 31
         }
      ]
 }

Then the alteration object could lift the +/-3 restriction. Perhaps there could be a restriction tied to the magnitude of the EDO. For example, 96EDO needs +/-16 to reach double sharp/flat. Basically, you divide the EDO number by 6 (discarding any remainder) to get the number of chromatic divisions of a whole step. In fact I am a little puzzled by the choice of +/-3 for 12-EDO. 2 alterations gets you to double sharp/flat in 12-EDO.

There are several popular EDO numbers besides 12: 19, 24, 31, 48, 96, and one or two others. With the continuingly greater prevalence of electronic music in all styles, their adoption is only increasing.

I mention these issues especially because MNX is being touted as a potential native format for a notation app. I am working on a potential export of Finale files to MNX. Finale has supported both non-linear keys and microtonal scales since its inception in 1989.