Sure...basically, especially when it comes to thematic music, or "main title" type stuff, it is a good idea to learn how to write in song form (AABA). There is a description of that reason, written by John Braheny that is very good so I will just copy his words here.
[ quote ]
by John Braheny
The form, also called the "format," "structure," or "formula," is a song's basic shape or organization. In the '50s and early '60s, there were hardly more than three different chord progressions (formulas) for any kind of rock music. If a song didn't conform to one of them, the odds were heavily against its becoming a hit, so the chord progression formulas perpetuated themselves. The 1-6m-4-5 (eg. C Am F G) progression spawned hundreds of hits like "26 Miles," "Silhouettes," and "Earth Angel." The twelve-bar blues format was also popular as it laid the foundations for rock and roll. (e.g. E- 4 bars,A-2 bars,E-2 bars,B7-1 bar,A-1 bar,E-2 bars)
Those old progressions were familiar enough to make us feel at home with new songs and new artists. They're predictable: the chords, the words and the tunes are different, but the basic shape of the songs is the same, so we can learn them quickly. Some basic forms and variations will continue as they have for many, many years for a simple reason: they work.
People have an unconscious desire for symmetry, and the repetition of rhyme, melody and form satisfies that need. The repetition of form also sets up a degree of predictability that's reassuring and comfortable to a listener. It sets up a solid base on which we can create surprises without taking our audience too far into uncharted territory.
The manipulation of form is a very important game to know. Classical musicians learn form as a basic part of their training, and for you, as a popular songwriter, to be able to make conscious choices about form is to be in control of your art. Once you understand the elements of form, what they do and why, you'll be able to challenge yourself to go beyond the familiar as you write your own songs.[/ quote ]
Now, a good technique is to use the basic song form structure...but one can make the chord progression a little less predictable by changing that up a little bit as you develope your themes. Now of course, all film music is not going going to follow this format...but whenever you have a chance to develope thematic material for something like a main title, or and end title, etc...it is a good idea.
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I thought I would drag up this thread again only to point out a great example of using song form in the underscore for a scene. In the new movie TROY, James Horner scored one of the scenes in that movie (the love scene with Brad Pitt and the Trojan priestess) using song form. If one listens to the underscore in this scene, it is almost an exact arrangement, for a lush string orchestra, of the pop song that runs during the end credits, with the melodic verses, chorus, bridge, etc...