HELP WITH TOUCH SCRIPT

Hi there,

I'm a little noob in Unity, right now I'm trying to make a guitar hero-like game for android. The thing is that I've got a good script to destroy the notes with a trigger (as they fall) but it is used with keys, and I'd like to trigger them with the touch. For example, when I touch the Circle on the screen just right when the note is getting to it I want it to destroy the note. Here is the script I'm using:

   public KeyCode key;
     bool active = false;
     GameObject note;
     SpriteRenderer sr;
     Color old;
 
 
 
     void Awake () {
         sr = GetComponent<SpriteRenderer>();
     }
     private void Start()
     {
         old = sr.color;
     }
 
     void Update () {
 
         if (Input.GetKeyDown(key))
             StartCoroutine(Pressed());
 
 
         if (Input.GetKeyDown(key) && active)
         {
             Destroy(note);
         }
                      
             
     }
     private void OnTriggerEnter2D(Collider2D col)
     {
         active = true;
 
         if (col.gameObject.tag=="Note")
         {
             note = col.gameObject;
         }
        
     }
     void OnTriggerExit2D(Collider2D col)
         {
         active = false;
         }
     IEnumerator Pressed()
     {
         
         sr.color = new Color(0,0,0);
         yield return new WaitForSeconds(0.1F);
         sr.color = old;
     }

So I'd like that instead of getting the key to trigger the destroy. It's triggered after having touched the object that has got this script.

Thanks in advanced for your help. <3