The useflag musepack of media-sound/moc does not work correctly as the configure script also checks for taglib >=1.3.1 before enabling musepack support. A dependency on media-libs/taglib should be added to the moc ebuilds when the useflag musepack is enabled.
+ 22 Apr 2010; Samuli Suominen <ssuominen@gentoo.org> + moc-2.5.0_alpha4.ebuild: + TagLib is required for Musepack support wrt #312783 by Christian + Glindkamp.