Apparently it's a common business practice. Spotify (even though I can't find any proof) seems to have build their software and business on pirated music. There is some more in this Article [0].
https://torrentfreak.com/spotifys-beta-used-pirate-mp3-files...
Funky quote:
> Rumors that early versions of Spotify used ‘pirate’ MP3s have been floating around the Internet for years. People who had access to the service in the beginning later reported downloading tracks that contained ‘Scene’ labeling, tags, and formats, which are the tell-tale signs that content hadn’t been obtained officially.
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