I’m not sure how the Options Controller and Music Player are able to access the PlayerPrefsController file. I was under the impression that a script had to be attached to a gameobject as a component and then could only be accessed by using the “FindObjectOfType” method.
The methods in the PlayerPrefsController class are static. Static things in C# do not need an object. You can access them directly. The disadvantage is that they cannot access anything that is non-static, for example, no objects in the Unity scene. The PlayerPrefs are static, though.