I think the best kind of music to put me in a certain mood is based by what kind of techno/trance/electronica song it is. These types of tracks are what alters my emotions the best. DJ Tiesto's In Search Of Sunrise: Asia is a good example of this. DJ Tiesto put together two CDs of trance music, the first disc being all mellow and easy on the ears, with a hint of asian flavor to it. That CD is a good one I listen to if I'm relaxing or readying to go to bed. The other CD represents the nightlife of Asia, and therefore is harder-hitting, faster paced, etc. That CD I usually play while I'm driving, playing video games, or while I'm trying to get into a better mode of concentration.