Using Grid-like singletons for continuous Audio

In my efforts to swap from singletons to @Fattie 's proposed 'Grid system' - I can't seem to get my audio continuing between scenes.

I thought that the instances are created in preload and everything the persists but I'm not observing that behaviour. Music just cuts off between scenes and I can't reference any of the Grid.controller.functions unless I create instances of them. I'm new to all of this..c# and unity so likely being a monkey somewhere! Thanks for any guidance.

My Grid.cs

 using UnityEngine;
 
 static class Grid
 {
     public static GameController game;
     public static AudioController audio;
     public static CameraController camera;
     public static BackgroundsController backgrounds;
 
     static Grid()
     {
         GameObject g;
         g = safeFind("manager");
 
         game = (GameController)SafeComponent( g, "GameController" );
         audio = (AudioController)SafeComponent( g, "AudioController" );
         camera = (CameraController)SafeComponent( g, "CameraController" );
         backgrounds = (BackgroundsController)SafeComponent( g, "BackgroundsController" );
 
     }
 
     private static GameObject safeFind(string s)
     {
         GameObject g = GameObject.Find(s);
         if ( g == null ) Error("The " +s+ " game object is not in this scene.");
         return g;
     }
     private static Component SafeComponent(GameObject g, string s)
     {
         Component c = g.GetComponent(s);
         if ( c == null ) Error("The " +s+ " component is not there.");
         return c;
     }
         
     private static void Error(string error)
     {
         for (int i=10;i>0;--i) Debug.LogError(" >>>>>>>>>>>> Cannot proceed... " +error);
         for (int i=10;i>0;--i) Debug.LogError(" !!! Is it possible you just forgot to launch from scene zero, the preload scene.");
         Debug.Break();
     }
 }

And my Preload...

 using UnityEngine;
 using UnityEngine.SceneManagement;
 
     public class PreloadController : MonoBehaviour {
     
         public static GameObject manager;
     
         void Awake() {
             DontDestroyOnLoad (manager);
         }
         // Use this for initialization
         void Start () {
     
         }
         
         // Update is called once per frame
         void Update () {
             if(Application.GetStreamProgressForLevel("GameTitle") ==1){
                 SceneManager.LoadScene("GameTitle");
             }
         }
     
     }

And my AudioController

 public class AudioController : MonoBehaviour {
 
     public static AudioController control; // TBH, not sure why I need this but complains about it being destroyed otherwise
 
 
     // CURRENTLY PLAYING MUSIC
     public AudioSource musicAudioSource;
 
 
     // MUSIC
     public AudioClip ocean;
 
     private bool isMusicMute;
     private string musicCurrentlyPlaying;
 
     void Awake() {
         control = this;
     }
 
         
     public void PlayMusicByStage(int stage) {
 
         switch (stage) {
 
         case 1:
                 PlayMusicByName ("ocean");
             break;
     
         }
 
     }
 
     public void PlayMusicByName(string name) {
 
         if (control.musicCurrentlyPlaying != name) {
 
             switch (name) {
 
             case "ocean":
                 control.musicAudioSource.clip = ocean;
                 break;
 
             }
 
             control.musicCurrentlyPlaying = name;
 
         }
 
         if (!control.musicAudioSource.isPlaying) {
             control.musicAudioSource.Play ();
         }
         if (!Grid.game.isMusic) {
             Mute ();
         }
 
 
     }
 
     public void StopAllMusic () {
         control.musicAudioSource.Stop ();
     }
     public void Mute() {
         control.musicAudioSource.volume = 0;
     }
 }