currently musepack/mpc files are only recognized as 'application/octet-stream'.
the file extensions for these files are .mpc, .mpp and .mp+
I would suggest 'audio/x-musepack' as the correct mimetype as this is also used
Ubuntu bug on this:
Created attachment 5229 [details] [review]
Ptch for a preliminary musepack support.
Works fine here
2006-08-25 Bastien Nocera <email@example.com>
* freedesktop.org.xml.in: Add a mime-type for musepack, patch from
Pino Toscano <firstname.lastname@example.org> (Closes: #6408)
on Aug 31, 2016 at 00:27:43.
(provided by the Example extension).