This paper has an interesting finding that makes me wonder (as usual). They found that happy or sad music doesn't make you more likely to look at happy or sad scenes (like in a movie). But the music does make you pay attention to the congruent parts for longer. So if there is sad music, you pay more attention to the sad scenes. And if there is happy music, you pay more attention to the happy scenes.
Where I wonder is how generalizable this is to our lives. We often play happy or sad music specifically to set a mood in our lives. But what if we have it backwards? When I am sad, sometimes I will play sad music and dwell in my funk. Maybe the music actually lengthens the sad spell. That would be unfortunate.