Hi there! I edited the lilypond-2.5.2.ebuild a bit, updated the deps and removed the "doc" useflag, as there was no way for me to build the documentation. There is a dependancy on mftrace-1.1.16 for which I just submited an ebuild http://bugs.gentoo.org/show_bug.cgi?id=104960 . This version is marked stable upstream, so except for gentoo-related things it might be OK to mark it stable eventualy. It built OK on my AMD64, but I have not used it very much yet.
Created attachment 67702 [details] lilypond-2.6.3.ebuild
*** This bug has been marked as a duplicate of 97574 ***