Did you know that 'old music' or catalog as they call it in the biz, is outselling new music? Catalog is defined as music that was released over 18 months ago. Here's a graph from Nielsen (warning, may contain facts) that shows this clearly.
This is very interesting. Polygraph* decided to venture into the data depths of Spotify (ahh, more facts) to find out what tracks are proving to be timeless.
*if you're struggling to open the link in Chrome, try Safari