I'm not sure how to respond to your post as you've made my point: The songs Mercuriadis has purchased the rights to are not passive income for him. See my response to your sibling poster.
Picture it this way - Mercuriadis has bought a bunch of houses. Just like any landlord, he will have to invest some money and effort into repairs and marketing his properties. Some will rent for more than he expected, some less.
But once he gets renting, it's passive income. The problem is, can he make it to that point or did he buy houses that weren't sufficently rentable?