Problems with music fonts

[David Bellows]

Hello everybody,

I am using LilyPond 2.23 but the problem I'm going to describe is
happening with older LilyPonds back 2.20.

I am running Linux (Pop_OS! 20.10 which is basically Ubuntu 20.10). It
is a relatively new installation on a computer I bought a few months
ago.

Here is the basic code:

\version "2.23.0"
#(set-global-staff-size 16)
\paper {
  #(define fonts
    (set-global-fonts
      #:music "beethoven"
      #:brace "beethoven"
      #:factor (/ staff-height pt 20)
  ))
}
{c' d' e'128}

With some music fonts this works, with others it doesn't.

Works:
Gonville https://www.chiark.greenend.org.uk/~sgtatham/gonville/
Arnold https://www.musictypefoundry.com/

Doesn't work:
Everything from: https://github.com/OpenLilyPondFonts
and: https://github.com/lyp-packages?page=1

I think all of those fonts on github are the same. Note, the Gonville
font in the latter two groups does not work while the one from the
website does.

When I try to compile the above code with anything from the "Doesn't
work" group I get the following error:

fatal error: unsupported font format:
/usr/local/lilypond/usr/share/lilypond/current/fonts/otf/beethoven.otf

Another data point. When I try to view any of the non-working fonts in
a font viewer, that also generates an error and nothing shows up. The
"working" fonts do show up in the font viewer.

So I'm guessing maybe there's something weird going on somewhere else
on my system? I don't know how LilyPond handles music fonts, but if
there's some kind of standard font library that it expects from Linux,
maybe mine isn't the right one?

Thanks,
Dave Bellows
https://www.platonicmusicengine.com