I didn't write this ebuild, but have confirmed it works, and am posting on behalf of the author, crs. Adds a useflag for 'moodbar' which includes a dependency on (the recently added to portage) media-libs/exscalibar.
Created attachment 79834 [details] amarok-1.4_beta1.ebuild with moodbar support
oops, better add the author's email... crs@wafel.com
This was already added in portage: 13 Feb 2006; Hanno Boeck <hanno@gentoo.org> amarok-1.4_beta1.ebuild: Moodbar / exscalibar support added. with the exscalibar useflag instead of moodbar. Please note that usually it's better to provide unified diff for ebuilds that gets changed, as that way it's possible to review the actual changes instead of having to check the entire ebuild.