Yeah, you can put it anywhere you want. I personally created a 'music' folder in the root where I put all my media files.
And you can go with the hierarchy (or structure) that iTunes created for you on your main computer, it's pretty efficient.. /artist/album/song is good enough for navigation.
One day, I'm sure the database will be updated to link to voice files. Or better yet, maybe someone will be able to port some text-to-speech engine, who knows?
Good luck
