Say you got hooked on a streaming service like Spotify, but you're hitting something of a wall -- 20 million songs is just too overwhelming and intimidating. Your playlists are stale. "The thrill is gone!" you wail. Cue Bluesify -- a Spotify app to browse and discover more than 100 blues artists in 28 subgenres, from pre-war and '30s Delta to Tom Waits and the White Stripes.