Ads for songs:
I'm not a professional YouTuber but I got a dmca notice for friends wedding playing I will always love you at the actual wedding.
I think the owners of that song got so many requests to do that and so many backlash against it that they decided to do ads for songs were they placed an ad on the video that's clickable in return for letting the video played the song.
I was considering giving everyone a 5 second theme song to my regular listeners. Since the music is copyrighted I've since held back. maybe ads for songs would be a good universal default program for short usage where the music is not the main attraction to the show.