I recently read an article about an internet radio station that allows the listener to select a playlist based on their mood. First Pandora allowed you to create a playlist based on an artist you like, now you can customize a happy, or a depressed playlist to suit your hour by hour emotional state.
This is the first I’ve heard of this in terms of the general listening audience. Because a producer of audio and visual works knows he has to think about the tone he is setting, music libraries like Royalty Free Music Library have been utilizing mood searches for years. For example, at the Royalty Free Music Library site, you can search for songs by keywords like Angry, Carefree, Fun, Inspiring, Heartwarming, Tense, and more. Setting the proper tone for your production with music is every bit as important as the visual elements.
So this new internet radio station is setting the playlist based on the mood. In our world, producers set the mood based on the playlist.