For instance, the Fresh Finds playlists - music that's good but very new or undiscovered - are made by curators who sift through songs and artists listened to each week by "tastemaker users". Spotify combs through their listener data and identifies users who have a habit of listening to music that later blows up and becomes much more popular. They tag those users anonymously and use their taste to inform the Fresh Finds playlists, which also feed the rest of the editorial department.
Really cool stuff.
https://news.spotify.com/us/2016/03/02/introducing-fresh-fin...
If you have songs in your playlist that someone else has in their playlist it'll find a song in that other playlist that you don't have. Offload the complexity of matching to humans already doing it.
Idk how that’s even possible but it happens once a month for me