Imagine the "Music" app is your default music player, but you want to change it to the "Play Music". First you need to clear the default application on your Android device as the music player.
To clear default apps on Note 4 do as follows:
1. Open Settings and go to the Applications tab
2. Tap to open the Default Applications options
3. Under the Clear Defaults menu, you should see the list of different activities and their default apps to open with
4. Find the function you want to clear, and simply tap the Clear button
5. For example, to clear the default music player, you need to find the Multimedia UI Service Layer option and clear it