“One of the problems … is keeping your music collection interesting. You’ll want to hear newer songs more often than older ones, yet at the same time you’ll want to make sure that the old music doesn’t get lost. You want to hear your favourite songs slightly more often than everything else, but you don’t want to keep listening to the same old tracks over and over again. As such you need to make sure your playlists have a good degree of variety as well as and a high churn rate. The way to achieve this is by utilising smart playlists, however it can be quite difficult getting the right balance.”