using manually installed fonts on OSX

[Kevin Patrick Barry]

Dear LilyPond users,

I have installed a font on my system (Cardo) and would like my musical
examples to use the same font as the document they will appear in.
LilyPond, however, doesn't seem to recognise that the font exists on
my system.  I can use it fine in LibreOffice, and XeTeX, and it
appears in my font book, where it is a user-installed font. Perhaps
that means it is kept somewhere that LilyPond isn't looking?

I tried running the fc-cache file in the LilyPond install, which just
returned an error, so then I removed the .lilypond-fonts.cache-2/
folder, which forced lilypond to rebuild the font cache (which took
some time). But after this the problem remains (and LilyPond defaults
to putting a sans serif font in place of Cardo).

In my googling I came across a reference to something called
fontconfig, which finds fonts on OSX apparently, but the
website/documentation for it is clearly written for people who know
something about computers (not me), and I couldn't understand any of
it.

Is there any way to get this font working in LilyPond?  It is a
TrueType font. I am using OSX 10.9.2 and LilyPond 2.18.  A minimal
example would be something like:

\relative {
  c_\markup { \override #'(font-name . "Cardo") text }
}

Thanks in advance,
Kevin