Object reference not set to an instance of an object

Hello im new to scripting and im getting an error trying to acces an component on other script a float value in a array i can figure out what im doing wrong please help and if its other ways of doing this

first this is the script that is accesing the value

 #pragma strict
 var audioSource : GameObject;
 var cancion : sonido = audioSource.GetComponent(sonido);
   
 function  Start (){
 
     if (cancion.band[6] > 0.3){
     
     Debug.Log ("mayor");
     }
 
  
 }

this is the second one that is getting accesed

 var freqData:float[] = new float[8192];
 
 var listener : AudioListener;
 
  
 
 var band:float[];
 
 var g:GameObject[];
 
  
 
 function Start()
 
 {
 
     var n:int = freqData.length;
 
     var k:int = 0;
 
     for(var j=0;j<freqData.length;j++)
 
     {
 
         n /= 2;
 
         if(!n) break;
 
         k++;
 
     }
 
     band  = new float[k+1];
 
     g     = new GameObject[k+1];
 
     for (var i=0;i<band.length;i++)
 
     {
 
         band[i] = 0;
 
         g[i] = new  GameObject.CreatePrimitive(PrimitiveType.Sphere);
 
         g[i].transform.position = Vector3(i,0,0);
 
     }
 
     InvokeRepeating("check", 0, 1.0/15.0); // update at 15 fps
 
 }
 
  
 
 function check()
 
 {
 
     listener.GetSpectrumData(freqData, 0, FFTWindow.Rectangular);
 
         
 
     var k:int = 0;
 
     var crossover:int = 2;  
 
     for(var i:int;i< freqData.length;i++)
 
     {   
 
         var d = freqData[i];
 
         var b = band[k];        
 
         band[k] = (d>b)? d:b;   // find the max as the peak value in that frequency band.
 
         if (i>crossover-3)
 
         {
 
             k++;
 
             crossover *= 2;   // frequency crossover point for each band.
 
             g[k].transform.position.y = band[k]*32;
 
             band[k] = 0;
 
         }   
 
     }
 
 }
 
 private var sqrt = Mathf().Sqrt;