Spotify's terms of service prohibit the downloading of music from their platform except through their official offline listening feature for Spotify Premium subscribers. If you're interested in listening to music offline, consider upgrading to Spotify Premium, which allows you to download tracks for offline listening within the Spotify app. This is the only legal and authorized way to download music from Spotify. You could also use some third-party Spotify music converters such as DumpMedia Spotify Music Converters, TunesFun Spotify music converters or TunesSolo Spotify music converters to do this.