Modulation is chaging the key signature or key center. The most recognizable one is direct modulation that is found in country and some pop music when at the end of the song during the chorus they raise the pitch by changing the key. It's stupid but is done a lot.
I just tried the link and it worked for me. Sorry for you. As far as direct modulation in country music being stupid, singing the chorus a 2nd or 3rd time in a different key just for the fun(?) of it is (I'm sorry) stupid. It never made any sense to me to do that.It adds nothing to the song. By the way it is not done a smuch as it used to be. I am a musician and teacher, so I have SOME knowledge of music. Just my opinion.