We all know music is an important component of setting the right vibe for role-playing.
Here are some of the factors I consider when compiling a playlist:
1. Fit the story - no rock'n'roll music in a high fantasy setting, folk music is not ideal for ShadowRun, etc.
2. I prefer not to have lyrics, but if there are lyrics they should support the themes of your story. I have several songs I've added to playlist because they match a character's situation or mindset perfectly.
3. No sudden loud, jarring changes - avoid music with trumpet blasts, drum fanfares and heavy metal ballads where the lead singer screams incomprehensibly for 30 seconds
I recommend the following:
For traditional DnD / medieval settings - Lord of the Rings soundtracks, the Fountain soundtrack, the Road soundtrack, Pan's Labyrinth soundtrack, Enya, Loreena McKennitt
For adventurous settings - Gladiator soundtrack, Last Samuri soundtrack, Battlestar Galactic soundtracks, Children of Dune soundtrack, Last of the Mohicans soundtrack
For horror/creepy settings - Nox Arcana
Light/Fun settings - Chocolat soundtrack
Future/ShadowRun settings - Transformers: Rise of the Fallen soundtrack, NIN, Paul Oakenfold (DJ), Break of Reality, Kopas, The XX
Random settings - Putumayo has various world music that can fit a lot of different settings
What are your favorite soundtracks/playlists to game by?