How to resolve ReferenceError: Error

I am building an mp3 playing in flash cs6 using actionscript 3. I keep receiving this error message

ReferenceError: Error #1065: Variable TCMText is not defined.

Here is my code: Note that the third variable "var isPlaying:Boolean = false;" is what is causing the problem because it worked fine before this. I am trying to prevent the audio from overlapping if the  play button is pressed again while it is already playing

var mySound:Sound;

var myChannel:SoundChannel;

var isPlaying:Boolean = false;

mySound = new Sound;

mySound.load(new URLRequest("media/OnImpulse.mp3"));

btn_play.addEventListener(MouseEvent.CLICK, playSound);

btn_stop.addEventListener(MouseEvent.CLICK, stopSound);

//pause_btn.addEventListener(MouseEvent.CLICK, runTracer);

function stopSound(myEvent:MouseEvent):void {

  myChannel.stop();

  isPlaying = false;

}

function playSound(myEvent:MouseEvent):void {

  if (!isPlaying) {

  myChannel = mySound.play();

  isPlaying = true;

  }

}