r/TrailerMusic

[From wiki:](http://en.wikipedia.org/wiki/Trailer_music)
Trailer music (a subset of production music) is the background music used for film previews, which is not always from the film's soundtrack. The purpose of this music is to complement, support and integrate the sales messaging of the mini-movie that is a film trailer. Because the score for a movie is usually composed after the film is finished (which is much after trailers are released), a trailer will incorporate music from other sources.