Well,
what I do is to have a custom tag called "Album Genre" which is not strictly musicaly related like the standard "genre" field. In this field I tag the albums as :
Movie Soundtrack, Concert, Show, Tribute, Compilation, Studio, Best Of, etc....
And the individual tracks are "genred" according to their musical content. e.g. "Jimmy Cliff - The harder they come" is tagged as reggae in the soundtrack album "The Harder they come" while "Jimmy Cliff - Many river to cross" from the same album is tagged as "Pop" (does not sound like reggae to me !). The "Album genre" tag for this album is "Movie Soundtrack".
This way when I setup a smartlist for random reggae tracks using the genre field, I really get reggae. (At least what sounds like real reggae to me !)
But that is just my personal feeling about albums/tracks genres, someone else might find my scheme akward.
Just my humble contribution to your question Wobbley,
Christian
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Listening to: 'Many Rivers To Cross' from 'The Harder They Come Soundtrack' by 'Jimmy Cliff' on Media Center 9.0