media-sound/lilypond installs some emacs stuff to /usr/share/emacs, even if emacs isn't installed. This is untidy. It should be use flag controlled (USE="emacs").
lilypond-2.10.25-r1 has Emacs support.
(In reply to comment #1) > lilypond-2.10.25-r1 has Emacs support. Thanks Ulrich. Lilypond needs to be stabilised then, when bug 178629 is fixed.