why we choose music to promote the films and television dramas

The use of popular music songs in films and television dramas is a good way to promote the popular media products. The songs are not only let audiences to understand the narrative more efficiently, but also let them remember what they heard during watch the media. As we know, “the relationship between music and film industries is ‘synergy’ and cross-promotion of media products”.
The aim of making soundtrack recording of the films and television dramas is not for creating stars, but can be observed to promote the visual media products. In fact, the soundtrack recording becomes a commodity to let people demand to see the visual media products and remember those longer.
Moreover, in my opinion, the reason why we consider the soundtrack recording as a better way to promote the visual image, is the MP3 players are much widely used than the MP4 players and also more convenient, people can listen to the music at anywhere and anytime. The pictures and posts are very convenient as well, however, they cannot last for a long time as music do (both the length of the music and the memory of the media) and cannot illustrate the emotional elements in the movie visual images.