Slightly off-topic: Do you know if Spotify (and other music streaming services) are allowed to accept payment to play/recommend songs for users? I am unsure if payola rules in the United States are strictly for radio stations.

They openly allow you to pay to put your songs in playlists, but they're marked as sponsored songs and users can opt out. Supposedly that's them following the rules; there are rumours of shadier deals going on as well, but there always are in the music industry.

That was 65 years ago. There are way more sophisticated ways now to influence things.