Josh has a Galaxy S4 that he likes, but the music widget keeps coming back and he hates it. Leo says that's not unusual. There's usually a default music player that Samsung uses. Leo says he can change the app on his lock screen in the display settings. That won't stop it from launching, though. Leo says one of the reasons he stopped using the Galaxy S4 is what he calls "Samsung interference."
The chatroom says all he can do is root it, install Titanium Backup and then freeze it. Another solution from the Galaxy S4 forums is to disable the app, and stop notifications. It should stop auto launching.
Samsung also sells a pure Google Play version that doesn't have all that nonsense. Leo hopes all of this will change with the S5, which will be announced Monday at Mobile World Congress.