Turn music off mutes music and sfx and sfx button doesn't do anything !! is something wrong with the script or might be something else?

 using UnityEngine;
 using System.Collections;
 using UnityEngine.UI;
 
 public class music_control : MonoBehaviour {
     [HideInInspector]
     public bool[] _music_fx = new bool[2]{true,true};
     public AudioSource _theme;
     [HideInInspector]
     public Sprite[] _textbuttons;
     float _vol_default = 1f;
     [HideInInspector]
     public Button[] _bt = new Button[4];
 
     void Awake(){
         _vol_default = _theme.volume;
     }
 
     public void _music_change(){
         if (_music_fx [0]) {
             _music_fx [0] = false;
             _bt[0].GetComponent<Image>().sprite = _textbuttons [0];
             _bt[1].GetComponent<Image>().sprite = _textbuttons [0];
             _theme.volume = 0f;
         } else {
             _music_fx [0] = true;
             _theme.volume = _vol_default;
             _bt[0].GetComponent<Image>().sprite = _textbuttons [1];
             _bt[1].GetComponent<Image>().sprite = _textbuttons [1];
         }
     }
 
     public void _fx_change(){
         if (_music_fx [1]) {
             _music_fx [1] = false;
             _bt[2].GetComponent<Image>().sprite = _textbuttons [2];
             _bt[3].GetComponent<Image>().sprite = _textbuttons [2];
         } else {
             _music_fx [1] = true;
             _bt[2].GetComponent<Image>().sprite = _textbuttons [3];
             _bt[3].GetComponent<Image>().sprite = _textbuttons [3];
         }
     }
 
     public void _play (AudioSource _sound, int _typ = 0){
         if (_typ == 0) {
             if (_music_fx [1]) {
                 _sound.Play ();
             }
         } else {
             if (_music_fx [0]) {
                 _sound.Play ();
             }
         }
     }
 
     public void _resetmusic(){
         if(_music_fx [0]){
             _theme.Play();
         }
     }
 }