What I want from a beat library

Have you ever found yourself listening to a song and wondering how the beat is constructed? Well, depending on what kind of music it is, you may or may not be well served by what's currently available on the web.

So what would a perfect beat library look like: perhaps most importantly, it needs to be complete (every song ever is a tall order, but why not aim high); it needs to have drum score and drum tab for all the beats; it needs to have user-playable files in midi format and proprietary formats such as fruityloops (this allows users to listen to the beat, but also alter it, which helps in understanding what makes it sound the way it does).

This data will also allow interesting comparisons between beats. For example, when you look up a beat the library can tell you "This is a characteristic