Having your “audioSource.play();” in the “if(Input.GetKey(KeyCode.W))” statement would cause the audio clip to be played every frame, its like opening a new music player and hitting play every frame. its going to sound like a bunch of jumble up sound, actually most likely will sound like one bad tone.
the instructor advises to put the “audioSource.Play();” in a if statement checking to see if that audio source is already being played, if true then it wont add another layer of audio clip.
example: (remember that “!” is not)
if (!audioSource.isPlaying)
{
audioSource.Play();
}