Is this a manually curated list of artists/music, or based on a Spotify API?

How does this tool pick which artist to display?

I created a searchable playlist of music based on YouTube content, but I'm pretty much adding musicians from a few select genres to it carefully-

http://www.ruffandtuffrecordings.com/SELECTIONS

I haven't really found a music suggestion tool that isn't driven by the creator's preference, would be nice if YouTube had better classification data on music that could be extracted by XML...