Spotify is a free program for your computer that allows you to listen to thousands of songs and make playlists without purchasing anything. All you need to do is listen to an occasional commercial. I try to have every song I post on tumblr also available in this Spotify playlist: Tumblr Songs
Unfortunately, not every song will appear since they aren’t on the Spotify service and only on my computer, so you’ll probably miss out on like 1 out of 10 songs I post. Still pretty good if you’re too lazy to click on each Youtube video I post.