Ok I've used this very briefly, and I like it. It does exactly what you are looking for. The only downside is that it organizes them into very basic mood categories, 10 to be exact, using colors to denote a happier or sadder mood. This link is only a demo, but i think its 10 dollars on the developer's website. Tell me what you think.
http://www.macupdate.com/app/mac/37199/chromatunes