Hello,

The attached patch adds MuseScore. It builds and lint doesn't complain.

I used glib-or-gtk-build-system because, somewhere in the Makefile,
there's a call to `gtk-update-icon-cache'. However, since that command
cannot be found during the build process, I skip it with
UPDATE_CACHE=FALSE. So, should I leave the package as-is, or add
a "gtk+" input, or simply downgrade to gnu-build-system?

Also, the description is a bit verbose. It is an excerpt from
Wikipedia's introduction about the software. Debian's is much terser.
FSF directory's is out of date. WDYT?

Regards,

-- 
Nicolas Goaziou                                                0x80A93738