Jonno said:
I'd just like to state here, once and for all, that a SONG is a piece of music with VOCALS. The term does not apply to instrumental music, such as film scores - piece/track/cue is fine, but not song.

Now please pass this on to the rest of the internet k thx.

Actually a song doesn't even need music but it does need words ex :

http://en.wikipedia.org/wiki/Song_of_Songs

http://en.wikipedia.org/wiki/Songs_of_Innocence_and_of_Experience

For me none of the music is scary as such but The Magic Tree is rather spooky especially with the sudden appearance of synthesised sounds (putting the piece out of the usual range of Star Wars Music), Padmé's Ruminations has some strange evocative sounds on there too.

If it's soundtrack music in general The Eggs (from Alien) and Night of the Electric Insects (The Exorcist) hit the mark every time.