Good luck! Spotify uses DRM to protect its music library, meaning the music files are encrypted. While you can download music for offline listening (with a Premium subscription), the downloaded files are still encrypted and only playable within a Spotify app. Of course, as with anything else, there are hacky ways around this but I do not think you will find anyone here willing to help you break the Spotify terms of service (could be wrong though). Revealing how to do so might also violate the rules of this message board but I am not 100% positive about this as I cannot find any guide lines/ rules regarding this.