One of the essential roles that soundtracks play in films is giving them personality. Remember that Once Upon a Time in The West has been used as a leitmotif. This is a musical phrase that is associated with a character, idea, or even place. It goes a long way in binding ideas and bringing attention to an already existing story. It helps the viewers relate with the character, and also helps the composer help the character stand out.
The idea of the soundtrack is to bring about a distinction in the events taking place in the film.