I use Foobar2000 on Gentoo with Wine. Maybe you can give it a try.
It works very well, it is an audio player for Windows with support for almost all audio formats and a built-in database, tagger with freedb support, file renamer. album list, converter, cd-writing with Nero libs..
It uses a pseudo-scripting langage with tags, so you can customize the display the way you want and is full of plugins.
http://www.foobar2000.org/For pure library, my fav. is mpeg audio collection, now open-sourced, but still for Windows (yep Wine). Simple and fill my needs.
http://mac.sourceforge.net/I look at JUK, seems to be a good alternative as soon as it will support more formats.
Maybe Gstreamer can be a good base for building such a tool. Qui vivra, verra.