RAP METATAGS?

So there was a brief moment where, listening to the Blakroc album's opening track, I found myself wondering whether ODB has been alive all this time and his death was an elaborate hoax, or whether the art of necromancy had been perfected and nobody told anyone. It turns out his appearance was just an unused vocal track, which leads me to wonder: if there's a pile of these unused vocal tracks just sitting around (my impression is that every (ex)member of the Wu Tang Clan has a vast stockpile of these somewhere), how does someone putting a new song together know which ones will be good for that particular song? Is there a system somewhere to keep all of this shit straight? Is there a vast library of unused ODB tracks that are tagged with metadata?

- 2:31
-- 4/4
-- 3 verses
-- 98bpm
-- weed, guns

- 3:12
-- 4/4
-- 3 verses, chorus
-- 102bpm
-- weed, partying

- 2:40
-- 4/4
-- 2 verses
-- 100bpm
-- weed, fucking

- etc

How else are they gonna know? I can't imagine any other way to get this shit done, but I'm not a producer. Who knows what they actually do.