The purpose of a work of fiction is to appeal to the lingering after-effects in the reader's mind as differing from, say, the purpose of oratory or philosophy which respectively leave people in a fighting or thoughtful mood.
We are uncomfortable because everything in our life keeps changing -- our inner moods, our bodies, our work, the people we love, the world we live in. We can't hold on to anything -- a beautiful sunset, a sweet taste, an intimate moment with a lover, our very existence as the body/mind we call self -- because all things come and go. Lacking any permanent satisfaction, we continuously need another injection of fuel, stimulation, reassurance from loved ones, medicine, exercise, and meditation. We are continually driven to become something more, to experience something else.
Traditionally, an engineer is responsible for capturing sound - microphone choice, gear, etc. A producer can have a number of different responsibilities - anything from songwriting to judging performances - setting mood, and (perhaps most importantly) choosing which songs to work on!
I remember when I first got the call from Beyoncé to work on the project, and the mood that she was in and she was feeling, she wanted New Orleans-inspired music to be incorporated to the stuff she was doing. Creole-type stuff. Zydeco... She wanted that type of inspiration.
As it is so strangely ordained in this world, what is amusing will turn into being gloomy, if you stand too long before it, and then God knows what ideas may not stray into the mind... Why is it that even in moments of unthinking, careless gaiety a different and strange mood comes upon one?