The Music That Moves You

What is it that makes a movie extra frightening, or jerks a tear from the manliest of men while watching a movie? Sure, it may be the ridiculously good acting, or the gory scenes. However, one aspect that is often overlooked in a movie is the music that accompanies those scary scenes or tear-jerking moments.
Have you ever watched a scary movie on mute? The haunting, jumpy scenes aren't nearly as frightening when there aren't string instruments building up the anticipation of that climax moment.
The significance of music in a movie was discovered tonight as I watched the movie "The Ugly Truth." While enjoying the comic film, I found myself tapping my foot to to the upbeat music as Katherine Heigl and Gerard Butler finally came together on a dance floor. It was the anticipated moment that the audience had awaited for the whole movie, and it would not have been as buoyant without the dance music playing in the background.
Without even realizing, my body was reacting to the song, naturally making me more on edge awaiting for a kiss between the to characters. If a simple song in a movie has this kind of effect on a person during a comic film, you can only imagine what impact music could make on someone to help promote a product, or better yet, a message.
Using music in something as simple as a 30 second commercial can be the deciding factor, which determines how memorable the message of that commercial can be. For example, the "Five, five dollar footlong ...." jingle used by Subway sent people humming their way into Subways around the country, linking the jingle with the knowledge that they were going to get a deal.
So, how do you decide what music to use in order to ensure it is memorable? Even more important, how do you decide which song will be memorable enough that when a person recalls it, it makes them think of the message or product you are attempting to promote?
These questions will be what I will attempt to explore over the next couple of days.