The Bonus Songs are chosen from the ones you probably won't know anyway - German, Japanese, etc. I've moved them from the normal game to a special part so they would not have a too great impact on those who have no interest or means to get them. They count only in the case of a tie in the normal game.
So, someone with a score of 17+3 beats a 17+0, but a 1+10 loses to a 2+0 despite technically knowing more songs. Of course, I doubt anyone could guess all 10 bonus songs. :P