How to disable a bool switch under certain circumstances?

Hey everybody,

For days I am looking how to solve this, without any success. I am trying to switch Sound on and off with a bool var. This actually works quit well. The problem is that I have four buttons that I can combine for different actions. So in my case, I would press button2 to enable certain possibilities . When I keep it pressed and now press button1 I can switch my sound on(or off(via bool)). That works well. If the sound is playing and I now press button3 I enable a Nightmode, that still works fine. But if I press button1 again and enable a "Night Action" the Soundbool turns on and off. But the sound should continue. The other way round works perfect. So if I enable the Nightmode first and then trigger the Night Action the sound keeps disabled. So I somehow need to disable the bool for the first possibility. This is my script which is attached to a master script:

 using UnityEngine;
 using System.Collections;
 
 public class KlassikScript : MonoBehaviour {
     public Masterscript masterParent;
 
     public AudioClip klassiko;
 
     void Start () {
     
     }
     
     // Update is called once per frame
     void Update () {
         if (masterParent.Song1Enabled == false){
             audio.Play();
             audio.loop = true;
         }
 
         if(masterParent.NachtErst == true){
             masterParent.Song1Enabled =false;
             audio.Stop();
         }
     }    

}

This is the part from the Masterscript:

 else if(pinValue1 == 1 && pinValue2 ==1 && pinValue3 == 0 && pinValue4 == 0){
             if(zweiterButtonZuerst == true){             //if button2 pressed first
                 Song1Enabled = !Song1Enabled;
             }
         }

I hope anybody has an idea what I might add?! Since it is a part of my final exam I really would appreciate your help!!! :-) Thanks!