Now, listen,here is the important part:
You do not play all four songs in a row,oh no.
You play the first song in a loop for days, every time you go to the loo. Maybe even place a loudspeaker with a motion sensor there.
Then you stop. And once they feel secure again, when they pull out their stupid phones again, then you strike again. With the same song!
Then,after a while you stop again. Wait for a while. Of course, they have learned and then expect the previous song again. But nooo! Another one,not one bit better than the first one.