What does Spotify cache in /Storage? ~/Library/Caches/com.spotify.client/Storage can get admittedly huge. I can't tell its contents due to the folder scheme. What are its criteria for storing things? Spotify also invariably stores more than I asked it to (in its settings). I saw that it used to cache local music (already on my hard drive, copied again), does it still do that? What else is in here? Is this remnants of a premium-only offline cache, or is Spotify caching everything I listen to anyway?
I think there's more question than answers there but it's Spotify's cache of files consisting of:


streamed music saved locally
imported songs (your local music)
adverts
metadata


The obtuse naming convention is purely a method to obfuscate the contents of the cache.

The cache is used in multiple cases, the main ones are:


to play already downloaded files instead of re-streaming (saves their bandwidth therfore saves $$$)
to allow Offline mode for Premium accounts