Soundtrack idioms in movies

I use the term "Soundtrack idiom" to mean a very short musical phrase that immediately informs the viewer that the scene has shifted to a new location, and also suggests where the location is. A cliché might be the opening bars of La Marseillaise to suggest that the current scene is in France. Or a guitar strum to inform the viewer that the scene is now in Spain.

But not every such idiom is taken from a national anthem, or even a previously published work. But they are almost always dead-on effective.

How are these 'idioms' composed? Is there a data bank that soundtrack composers can refer to?

Best Answer

Summary:

Yes, there are data banks film makers can refer to.
Often the music on these sites is composed by relatively unknown composers.
It seems extremely likely these sites also contain location music.
This type of music is called production music

Detailed:

I'm only going to answer part of your question, as the truth is I can't categorically comment about location themed music. However, I can answer regarding a data bank of music and it seems logical to assume that location themed music is found there, along with all manner of other clips (although I can't verify this without actually signing up to one of the many sites).

Effectively what you are referring to is production music:

Production music (also known as stock music or library music) is the name given to recorded music that can be licensed to customers for use in film, television, radio and other media. Oftentimes, the music is produced and owned by production music libraries.

Unlike popular and classical music publishers, who typically own less than 50 percent of the copyright in a composition, production music libraries own all of the copyrights of their music. Thus, it can be licensed without the composer's permission, as is necessary in licensing music from normal publishers. This is because virtually all music created for music libraries is done on a work for hire basis. Production music is a convenient solution for media producers—they can be assured that they will be able to license any piece of music in the library at a reasonable rate, whereas a specially-commissioned work could be prohibitively expensive.

To give more insight on the Work for Hire term:

According to copyright law in the United States and certain other copyright jurisdictions, if a work is "made for hire", the employer—not the employee—is considered the legal author. In some countries, this is known as corporate authorship.

So among the work that production libraries store (taken from the first link):

Production music libraries typically offer a broad range of musical styles and genres, enabling producers and editors to find what they need in the same library. Music libraries vary in size from a few hundred tracks up to many thousands...Library music is frequently used as theme and/or background music in radio, film and television...Library music composers and session performers typically work anonymously and have rarely become known outside their professional circle.

The way this works is based on two different types of income streams:

License fees (paid upfront to library for permission to use music).
Performance income (generated when music is performed publicly, e.g. on tv/in movies).

For some information on the market in which these groups can be found:

The production music market is dominated by libraries affiliated with the large record and publishing companies: KPM is owned by EMI; Universal Music Publishing Group library music has the music libraries Chappell, Bruton and Atmosphere under their own name as well as others owned by them such as FirstCom and Killer Tracks; Imagem Production Music (formerly Boosey & Hawkes Production Music and including the Cavendish, Abaco and Strip Sounds labels) is owned by the Imagem Music Group; Extreme Music is owned by Sony/ATV Music Publishing; and Warner/Chappell (a division of Warner Music Group) owns Warner/Chappell Production Music.[4] Established in 1965 Sonoton is the largest independent production music library in the world. There are numerous smaller libraries.

So to answer some of your questions:

These are composed by a collection of often unknown composers who rarely become household names, working for a variety of production music companies.
There are various data banks film crews can refer to when looking for appropriate production music.

As to whether these sites contain music on location music, I feel the answer is probably yes. Some basic research on these sites seems to suggest so. For example, AudioNetwork state:

Background Music often refers to the unobtrusive tunes heard in a lift or in a restaurant, and can be another term for musak, piped music or weather music.

To many people however, it’s just another name for a musical soundtrack, a bed or an accompanying composition on a:

TV show
Feature Film
Corporate Productions
Advert.

While background music can be almost entirely un-noteworthy, it can also:
create atmosphere
generate mood
prompt & provide narrative

The final bullet point, about providing narrative, is certainly something that a location theme change would do.

On a final note, it appears many of these sites work in one of two ways. You can either:

Browse their catalogue and find a piece of music you like, then detail exactly how it will be used so royalty calculations can be created.
Submit a request for a piece of music to suit a certain scene which you describe.