Just run. Don’t even bother.
Playing out of catalogue music in the house via the desktop app is not a problem when the music is stored in my Windows Music folder for easy access and recognition by Spotify. Getting them to mobile is possible but an exercise in frustration. Overly complicated. It took me a couple of hours to get working.
- Spotify Desktop: Settings | Your Library | Show Local Files = On
- Spotify Desktop: Settings | Show songs from | Music Library = Off. Recommended for while you set up and test otherwise there are duplicates and Spotify does not let you know if you are looking at a .flac or .mp3 version of a file.
- Create a new folder outside of the Windows Music folder for MP3 versions of my files. Mine is called Spotify Music.
- Spotify Desktop: Settings | Show songs from | Add a source - select the folder created in the previous step.
- Spotify Desktop: Create a playlist for each album you want to transfer to your mobile device. This playlist can be anywhere in your hierarchy. If you already have a playlist for the .flac files you will need another.
- Spotify iOS: Settings | Local Files | Show audio files from this device = On. I’m not 100 sure if this is required, but it helps you see which files are actually on your device. Although you can control playback on another device for .flac files, you can’t play them on your mobile.
- Spotify iOS: Allow access to local network devices. You can set this via the iOS settings for Spotify later if you missed it or don’t get prompted.
- Spotify iOS: Go to the playlist you want and download it. Repeat for all other albums.
If you have added the .flac file to a playlist it will appear to download OK, but won't actually be there to play.