I'm curious whether you think this might be an appropriate question to ask on Web Apps:
What artists are not available on Spotify?
I asked it at Music Fans, where it was closed for well-meaning, but I think misguided reasons. You can read those reasons in the comments at the OP, and also in this extended Meta discussion:
This is a question that I will personally receive great value from, and I think it will provide significant value to the internet as a whole. Stack Exchange is uniquely positioned to host a question like this. Our platform wasn't built for list questions, but it works for them, and there are numerous exceptions across the network where it's been demonstrated they can thrive. I think this might be one of those exceptions, but there's only one way to find out.
I'd be grateful if you gave the question a chance, but also I understand it might not be welcome here either. I'm willing to moderate it myself (since as OP I'd receive inbox notifications). If you feel the risk of spam is too great, we can "protect" the question, though I'd rather give it a chance to live in the wild and see how big a problem spam really is.
Looking forward to your thoughts.