In the past, I've used Lukas Pietsch's Black Mensural plugin
(http://www.lukas-pietsch.de/Music/blackmensural.ly) to set black mensural
notation. It works pretty well with Lilypond 2.12, but less good on newer
versions of Lilypond. The spacing and whatnot is often way off, for
example,
with noteheads colliding into one another, and ligatures frequently don't
work. I'm pretty sure there were some changes in Lilypond 2.14 to the
mensural plugin, which breaks certain aspects of the plugin.
(Lukas's original thread introducing the Black Mensural stuff is at
http://lists.gnu.org/archive/html/lilypond-devel/2011-01/msg00088.html)
I'm willing to work on his plugin to get it to work properly on recent
Lilyponds, but I'm not very familiar with Lilypond internals, especially
when
it comes to the mensural stuff. I'm hoping that someone here with more
knowledge might be able to lend a hand, or at least point me in the right
direction as to where would be a good place to start.