I hadn't heard of Anna's Archive before. Apparently their focus is usually books and papers. They explain why Spotify and how here:
While there's likely to be a lively debate between lawyers over the legality of helping themselves to Spotify's audio library, the data is fascinating as well. Here's the 10,000 most often-played songs on Spotify as of the date they scraped:
Backing up Spotify
We backed up Spotify (metadata and music files). It’s distributed in bulk torrents (~300TB). It’s the world’s first “preservation archive” for music which is fully open (meaning it can easily be mirrored by anyone with enough disk space), with 86 million music files, representing around 99.6% of...
annas-archive.org
While there's likely to be a lively debate between lawyers over the legality of helping themselves to Spotify's audio library, the data is fascinating as well. Here's the 10,000 most often-played songs on Spotify as of the date they scraped:
