Mute audio with GetKeyDown

What I have, is a script that starts playing a looped sound when I enter a trigger. This is a attached to a ladder, so only when the player climbs the ladder and is inside the area of the trigger, the sound plays, and mutes itself when the player leaves the trigger. However, I need the audio to mute also if the player stops climbing the ladder halfway up.

Here's what I have so far

 function OnTriggerEnter (other : Collider){
   if (Input.GetKey(KeyCode.W)) {
      
     if(!audio.isPlaying) {
       audio.loop = true;
       audio.Play();
 
     } if(audio.mute) {
     audio.mute = false; 
 }
 }
 }
 
 function OnTriggerExit (other : Collider){
     audio.loop = false;
     audio.mute = true;
   }

This plays the audio while pressing "W" (the key used for climbing up) inside the trigger, and stops looping and mutes it when the player leaves. But I need it to also stop playing when the player stops pressing "W" to stop midway on the ladder, while still inside the trigger.

Does anyone know how to do something like this?