I'm trying to understand the App Store Review Guidelines around the Apple Music API. However, I can't seem to find a definition for the Apple Music API, and in particular how far it extends (i.e. how much of the entire API does it encompass?).
On this iTune Affiliate Resource page it is suggested that the Apple Music API is a combination of:
The point of the language you quote in your comment is merely that you must not try to do what Apple is already doing, i.e. make money by getting the user to subscribe to or access Apple Music (the online streaming service) through you rather than Apple. You aren't going to do that, so don't worry about it.
EDIT I'll give you an example of what Apple is saying you cannot do. Let's say you have an app that plays music from the user's library, and that you differentiate: you say, to play your music is free, but play Apple Music songs will cost you an extra dollar of in-app payment. That would be a violation of the rules.