MB has every option out there to filter the library. But I was thinking that there could be other interesting ways to browse the library, not only based in filtering.
Instead of filtering according to conditions and getting a list, just surfing the library more as a 'explorer'.
I think that it could implemented using a kind of 'tree' view in the main panel. I have made a example using excel, but it's easy to see how it works.
Imagine you start with an artist, let's say Brandi Carlile. Then you have different option to explore. I have selected four (though there could be more): albums from this artist, albums where this artist appears but are compilations (album artist is different), similar artists according to Last.FM, and compilations where similar artist according to Last.FM appear.
Those options can lead you to different artists, and those artists to other artists, and so. So you can 'surf' the library advancing through relations, instead of just filtering.
Here there's an example of what I'm saying: