Aaron Parecki

Have you ever wondered what other songs used the same chord progression? This is kind of an amazing site that will tell you: http://www.hooktheory.com/trends

Pretty sure Spotify's Discover Weekly works specifically because of the constraint they set up for themselves. It's updated once a week, and there is a finite number of songs in the list. With other services, people turn on the "recommended" station and expect an infinite stream of music that they will like.