Being a kid, as all kids do, you feel out of place or like kind of a freak. You wake up feeling like your head got put onto someone else's body that day.
Let's say music is needed for only 43 seconds of film. You have to score it so it is an entity, so it won't bother anyone when it ends so quickly. Or if a song runs 2 minutes and 45 seconds, but the titles run a minute longer, you have to arrange that song so it doesn't get repetitious.

