I have personally found some of my favorite songs and artists through movie soundtracks, and viewers really do make emotional attachments not only to the movie itself but also to the music that is chosen for the movie. This articles discusses how soundtracks may be overlooked, but can be very beneficial for music promotion.
Twilight is probably the best example considering its popularity and the fact that people are already waiting to see the rest of the movie series and to hear what music will be showcased. As much as people say the music industry is suffering, which may be true, it is important to remember the outlets such as soundtracks. Although they may not take first row to promotional strategy, it could be just as important and beneficial.