Many of the earliest musicals, such as The Wizard of Oz (1902), included songs from a variety of sources that might change from one production to another. However, Showboat (1927) introduced the idea of the book musical, in which songs, vocal ensembles and dances are fully integrated into a plot with serious dramatic goals.

Some of the most famous and iconic musical of the decades that followed, most of which are still performed today include:

The modern picture industry developed in the early decades of the 20th Century, but films did not have a soundtrack until the late Twenties. Instead, music was provided by a pianist in the cinema to cover the noise of early projectors.

It was soon realised that music could enhance the visual drama. Cue sheets were published for each new film to provide pieces to play or ideas on which to improvise, for the various scenes in the film.

Larger cinema installed pipe organs that were played for entertainment before the film as well as to accompany the pictures and the very largest cinemas employed small orchestras for the same purpose.

By 1930, most films had a synchronised soundtrack and directors quickly became aware of the power of music to:

• create a mood

• suggest a place of historical period

• provide a transition between different scenes

• remind the audience of previous event, characters or ideas through the use of recurring leitmotifs

• Dictate the pace of the action.

Soon composers were being commissioned to write original film scores, one of the first being for King Kong (1933). It was written in an exciting Romantic style for an 80 piece orchestra by Max Steiner who would go on to compose over 300 film scores.

From the Forties onwards, the scores of American-born composers Bernard Herrmann and Leonard Bernstein introduced a harsher, more contemporary edge to film music.

The Fifties saw the use of jazz in some film, not only making the soundtracks seem more modern, but also acting as an economy measure, because engaging a jazz band of a few musicians for several days of recording was far less expensive than hiring a full symphony orchestra.

From the Sixties onwards film scores have included such diverse styles such as rock music and experimental electronic music.

The complete set of original music to accompany a film is called the 'Film score' and it forms part of the films 'soundtrack' (which also includes the spoken dialogue and sound effects)

Each individual piece in the score is known as a cue and is timed to begin and end at very precise timings during the film.

The main title is the music heard during the 'opening credits' of a film. Because the credits usually slowly scroll by, this is sometimes known as the 'opening crawl'. The music acts like a short overture, setting the mood for the opening of the film. In some cases (James Bond) a film might start with a theme song rather than with instrumental music.

The end credits are normally longer as they list all the personnel involved in the production, and also have a musical accompaniment, which may or may not be similar to the main title.

During the film itself, there are two main types of music:

• Diegetic music - sometimes called source music, is music that comes from an on-screen source and so occurs as part of the action in the film, such as when a character turns on the radio or hears a group of street.

• Non-diegetic music - sometimes referred to as background music or underscoring is heard only by the audience and is used to set the scene, establish the mood or underline the drama or the situation.