It depends on your definition of “manually copy”. The file system on iOS isn't exposed, so you can't browse around in the files and folders and copy it somewhe

It depends on your definition of “manually copy”. The file system on iOS isn't exposed, so you can't browse around in the files and folders and copy it somewhere there. Instead, each app has its own little container with files, so you can use iTunes on Windows or Finder on macOS to copy it into either a specific app’s container or the Files app’s container. If you do the latter, then you can access it on the device via the Files app and third-party music players. The stock Music app provided by Apple doesn't get access to the files in the Files app. Instead, it maintains its own library synced with other devices, with the option to import your music files into that library. The optimistic reading of this is that this prevents apps from accessing files that they have no business looking into. The pessimistic reading is that this prevents users from messing around with files and prevents them from tweaking or hacking apps. I think the truth is a little bit of column A and a little bit of column B.