Hi, 

Years ago, someone asked me to write a song for a movie they're making. They released a soundtrack which was eventually added to Spotify. It's a pro bono contribution and I never expected anything in return.

I don't have a label and have never considered selling/uploading my music anywhere. Lately, however, I've been thinking of using one of the aggregators to upload some more music. My question is, how can I link that one song that's already on spotify to the account I'm making? Or...if my song was uploaded, does that mean there's already an artist account? How can I have access to it?

Any help would be greatly appreciated.