How to use Lazy Singletons in C#

LazySingleton.cs

public class MusicManager : MonoBehaviour 
{
    //We make a static variable to our MusicManager instance
    public static MusicManager instance { get; private set; }

    //When the object awakens, we assign the static variable
    void Awake() 
    {
        instance = this;
    }

    public void Play()
    {
        //Play some audio!
    }
}

//...
//Now in another class, we can call Play() by using the static variable!
public class LevelController : MonoBehaviour
{
    void PlayMusic()
    {
        MusicManager.instance.Play();
    }
}