Is it possible to use the Spotify offline songs that already been downloaded to my iPhone with vox? It seems to be streaming the songs I’ve already downloaded to my phone (Spotify)
No, those files have DRM.
Spotify is available for online streaming with VOX, but not for downloading your music on your device.
Only Spotify users can download their music for offline listening using Spotify Music Base, but not any other application yet.
If you have downloaded Spotify tracks on native, you will find that these files are in OGG format, which means Spotify songs are encrypted by DRM technology, we can’t directly play them!
If you would like to sync Spotify`s downloaded songs to some 3d party app.