The Lullaby (Main Gaon Tu Chup Jo Ha)
In rewatching looking to find the shaved facial hair scenes, I suddenly paid attention to this song for the first time. Totally un-subtle, but look at what's happening. All nature is singing this lullaby, especially with the rubbing twigs being a violin, and the spider webs, and wind blowing the window.
As I say, it's kind of slap in the face obvious, but I had not paid attention before. Fun.
http://www.youtube.com/watch?v=kOGFWa7YPZE