Cinema music began as a way to not only drown out the sound of the projectors, but to also create an emotional backdrop for the characters. As filmmaking developed, music also progressed, from the use of a single piano to a trio, to a salon orchestra and then to a full symphony orchestra. Cinema organs, which initially made up for the lack of woodwinds, were equipped with stops for sound effects such as drums, airplanes or a child crying.
The underscore of a film is more commonly referred to as the "background music." These types of compositions are the most taxing on film composers, because films have strict deadlines and timetables. The underscore is the majority of the music used in the film. It is used during chase scenes, under dialogue, to set up romantic scenes and the basic theme of the film. Many times a full orchestra will be used, but other times it can be a small chamber group, a soloist or created on computers.
The use of pre-existing hit songs can help studios promote a film; also, a carefully selected song can set a period piece, give the actor a chance to sing and generate income through soundtrack albums and singles. Film producers must obtain permission from the music publisher to use the song in the movie, trailers, television and radio promos.
Some of the most difficult compositions for any composer or lyricist are those songs made specifically for the film. Composers are given a brief description of the film, the specific placement of the song and subject matter. Contracts are drawn up with composers generally paid a fee plus royalties in exchange for full rights, including editing rights for the studio. After the song is composed, a lyricist might be hired to make changes.
The use of silence, or absence of background music, is effective for filmmakers only when other sounds are naturally occurring in the film. Silence, considered an acoustical effect, is important to recognize in its role in film because no other art medium can present silence to an audience. Even in silence, feelings can be conveyed in an actor's facial expressions and body language. Using silence gives significance to the scene and creates tension within the film.