Draft: Extended mensural notation support

[Lukas Pietsch]

Dear Lilyponders,

a few of you might remember a set of extensions I once drafted for enhanced
mensural notation support in Lilypond, including black mensural notation.
I've been working on this project on and off in the meantime and now have
something far more stable and technically mature (I hope) than when I first
presented it here.

Recently I have been in contact with Prof. Giuliano Di Bacco of Indiana
University, who has been discussing an exciting project with me. They
consider using Lilypond, with mensural extensions, as a rendering backend
for the display of medieval notation snippets contained in a large corpus of
medieval writings on music theory, the "Thesaurus Musicarum Latinarum"
(TML). The notation samples, which include numerous highly uncommon and
idiosyncratic forms, will be encoded in the corpus in an XML-based format
(an extension of the "Music Encoding Initiative", MEI), with a script to
transform them into Lilypond code for rendering. The University might offer
a bit of funding for completing the Lilypond extensions and writing the
conversion script.

I have a working draft of the Lilypond coding, which involves quite a bit of
Scheme code, a patched Lilypond font with a section of new proposed glyphs,
and a few minor patches to Lilypond's C++ codebase. Unfortunately, owing to
the latter, the whole system currently works only with a patched,
custom-compiled Lilypond installation. I'd like to hear if there's interest
among the Lilypond folks to merge these extensions into the standard
distribution, and how best to proceed to do so.

I am putting up a zip file with the current Scheme files and fonts and a
documentation file with sample illustrations at
https://www.dropbox.com/s/nrcz11hkslsbc52/custommensural-2015-02-23.zip?dl=0 

Comments will be highly welcome!
Best,
Lukas