How to adjust In-Game volume in C#?

Hello! I am currently trying to figure out how to adjust the In-Game volume via a GUI Slider. I've done this before, but my hard-drive was wiped so I lost my script and a lot other files. I remember that I used a hSliderValue to adjust a AudioSource component to turn the volume up or down. How would I do this? I wrote some code to attempt this but it did not work. Here is the code(In the "AudioOptions" void) using UnityEngine; using System.Collections;

 public class GUI_menu : MonoBehaviour {
     private string CurMenu;
     public float hSliderValue = 0.0f;
     // Use this for initialization
     void Start () {
         CurMenu = "Main";
     }
     
     // Update is called once per frame
     void Update () {
         AudioListener.volume = hSliderValue/10.0;
     }
 
     void ToMenu(string menu)
     {
         CurMenu = menu;
     }
 
     void OnGUI()
     {
         if(CurMenu == "Main")
             Main ();
         if(CurMenu == "Options")
             Options ();
         if(CurMenu == "GraphOptions")
             GraphOptions ();
     }
 
     private void Main()
     {
         if(GUI.Button(new Rect(0, 0, 128, 32),"Play Limp"))
         {
             Application.LoadLevel("Level 1");
         }
 
         if(GUI.Button(new Rect(0, 36, 128, 32),"Options"))
         {
             ToMenu("Options");
         }
     }
 
 
     //Option menus
 
     private void Options()
     {
         if(GUI.Button(new Rect(0, 0, 128, 32),"Graphic options"))
         {
             ToMenu("GraphOptions");
         }
 
         if(GUI.Button(new Rect(0, 32, 128, 32),"Audio options"))
         {
             ToMenu("AudioOptions");
         }
     }
 
     private void GraphOptions()
     {
         if(GUI.Button(new Rect(0,0,128,32),"Very Low"))
         {
             QualitySettings.currentLevel = QualityLevel.Fastest;
         }
         if(GUI.Button(new Rect(0,32,128,32),"Low"))
         {
             QualitySettings.currentLevel = QualityLevel.Fast;
         }
         if(GUI.Button(new Rect(0,64,128,32),"Good"))
         {
             QualitySettings.currentLevel = QualityLevel.Good;
         }
         if(GUI.Button(new Rect(0,94,128,32),"Default"))
         {
             QualitySettings.currentLevel = QualityLevel.Fantastic;
         }
         if(GUI.Button(new Rect(0,126,128,32),"Very Good"))
         {
             QualitySettings.currentLevel = QualityLevel.Beautiful;
         }
         if(GUI.Button(new Rect(0,164,128,32),"Back"))
         {
             ToMenu("Main");
         }
     }
 
     private void AudioOptions()
     {
         hSliderValue = GUI.HorizontalSlider (Rect (370, 220, 546, 30), hSliderValue, 0.0, 10.0);
     }
 }

Any help? Thanks in advance! :D