Although many moviemakers acknowledge the importance of music to the emotional impact of a movie, it is not always understood how to go about getting the right music in the sound track.
Unfortunately, many moviemakers make a connection between the term “sound track” used by marketers to sell a collection of songs used in a motion picture and the term “sound track” that we use to define the elements that accompany picture in a movie. These leads many amateur moviemakers to seek out pre-recorded songs, usually by popular bands, to paste in as wallpaper in their motion picture.
This is a bad idea of two reasons. The first, and least important, is that it is illegal. Yes, even in an amateur film, and yes - even in a student film. It is illegal to use a copyrighted piece without permission. You can seek permission from the rights holder and it is not as difficult to obtain as you might imagine. Even if you didn’t want to obtain the rights, we might wink and nod at using a song without permission if it was actually an effective tactic. It is not.
If you listen to how these kinds of songs are used in a Hollywood picture, you will realize they are not used as wallpaper. Even when a popular song is used in a big budget movie, usually only part of the song is used in a scene transition or an action sequence. An entire song might be used for a montage or the opening and closing credits. It is not pushed into the movie to drone on and on in the background under dialogue.
This is the second reason why you shouldn’t use popular songs in your movie: the emotional beats of the music is not going to match the emotional beats of your movie. You can retime your images to match the music but then you will have a music video.
Presumably, you have an original story to tell and don’t want to make it conform to someone else’s concept using someone else’s timing and structure. If you have your own story to tell, you will want the music to conform to the picture not the other way around.
To do this, you will need to identify the emotional moments in your piece, the turning points, the climaxes of scenes, the critical lines of dialogue. One can refer back to the dramatic curve to help identify these moments, called “cues”. A piece of music that is designed around cues that are in sync with events on the screen is called a “score”. A score is created by a composer.