Have you ever wondered how to get a remix you found on youtube to your spotify playlist when it does not exist on spotify?
I'm going to tell you how you can do this! THIS NEEDS TO BE DONE ON THE COMPUTER!
First off you need the mp3 for the song. Download this if this is available. If you downloaded this through your browser the file should now be in "downloaded files".
Good, now go to the spotify application and locate "local files" under "your library". Find the name of the mp3 here and add it to your desired playlist. Download the playlist so that you can listen to it offline. To listen to it on your phone you need to download the playlist there aswell.