I use Spotify unlimited with a bunch of playlists I've put together from DMing for a few years, I'm really quite proud of it. I usually pull up a youtube 10-hour loop of a sound effect that covers the general area the PC's are in as well. For example, I play a "10 Hours of Blizzard" or something if they're in the mountains, and then I turn that relatively far down, and then I play music which I pick depending on what the current happenings are. Other ambient noises could be rain, hail, livestock, people in a city, or a sandstorm for examples. Cave drippings and such make great dungeon ambient noise as well.
I have a playlist for monologues which I am most fond of, great for reading my little intro-speeches or for when characters explain their dark pasts or misadventures.
I have a playlist for towns, both sad and happy, playlists for combat, and taverns, stealth segments, chase-scenes, and then default one-sized-fits-most songs. Most of them are from game or TV soundtracks.
There's my battle list, it increases in intensity as you go, so it starts cutesy and ends epic. I also use a fader that you can change in the options that makes the transitions between songs pretty seemless. I try to use songs that transition well.
That's my monologue list, it's something that I attempted to organize by "For DM's" and "For Players" but really it just works best to know all of the songs and know which songs go best in which situations. For example, "Old Friends" from Darren Korb is an incredible flashback Batman-style song for PC's to monologue off of. "Human Qualities" from Explosions in the Sky is great for describing a dream or something of that nature.
I really feel like this adds so much to the experience. I never get quite as into the roleplay if intense music isn't accompanying it. If I'm roleplaying a dying captain on a ship and the PC's are trying to revive me, normally I'd just describe what's happening, but under the right musical conditions, I go straight thespian, haha.
Here are a few others:
Standard town - http://open.spotify.com/user/1217314767/playlist/6AImjJ8M6cfSN0CzERCoph
Sad town, maybe destroyed by orcs and trying to rebuild or the like - http://open.spotify.com/user/1217314767/playlist/0R2a4KuhSCPjwqWasA6kw9
Bars and Taverns - http://open.spotify.com/user/1217314767/playlist/2Fwt89kpSIWn7RndJ4JqC6
Dungeons, this is also good default adventuring or description music - http://open.spotify.com/user/1217314767/playlist/251dZQrVBmoeEEWXxX6QGk
Success music! This starts as cheesey "Yay you did it" music and meanders into a kind of "You did it... but at what cost?" - http://open.spotify.com/user/1217314767/playlist/1tyv598xsq9gGMupv9YxIX