Singletons in music script?

Ok, I've been searching around for awhile for a music playing script that continues across scenes but destroys when it returns to the first scene, I finally found one. But this script calls for MyUnitySingleton, which first of all I have no idea how to declare or make a singleton for it to reference to. Here is the link to the code.

http://answers.unity3d.com/questions/11314/audio-or-music-to-continue-playing-between-scene-c.html

I don't know what the MyUnitySingleton is that they are referring to. I'm trying to use the second commented code:

The first function:

 private static var instance:MyUnitySingleton;
 public static function GetInstance() : MyUnitySingleton {
 return instance;
 }
 
 function Awake() {
     if (instance != null && instance != this) {
         Destroy(this.gameObject);
         return;
     } else {
         instance = this;
     }
     DontDestroyOnLoad(this.gameObject);
 }

And the second:

var NewMusic: AudioClip; //Pick an audio track to play.

 function Awake ()
      {
           var go = GameObject.Find("Game Music"); //Finds the game object called Game Music, if it goes by a different name, change this.
           go.audio.clip = NewMusic; //Replaces the old audio with the new one set in the inspector.
           go.audio.Play(); //Plays the audio.
      }

Help on what a singleton is, how to make one/declare one, and how to get this script to work would be great.