Variations on a Theme

So I had this song stuck in my head.  After trying--and failing--to excise the tune from my brain, I just let my mind do its own thing and I found myself thinking more and more about movie themes.  Not instrumental themes, but theme songs.  Songs custom-made for film, that play over the credits and are only available on the soundtrack.  You know, like how every James Bond movie has its own song.  That kind of thing.

I thought, you really don't hear a lot of those any more.  And it's a bit of a shame, really.  While the songs themselves aren't all winners, their presence helps complete the package; the film as product.  What prompts a producer to pursue a special-purpose song?  It's all part of a film's marketing--radio play certainly helps keep the film front-of-mind.  And casting a singer in a major role generally ensures a unique musical composition.  Conversely, an actor might seek to expand into music by lending their voice to the film's soundtrack.

Some movie themes are awesome.  Others, not so much.