I loved to use the rain song so that mill wuld go faster. He always wants to play at the same speed, so when you do that, he has to play FAST and if you talk to him, he is angry at you.
The scene would have worked better if they hadn't show the gun in the trunk of his car beforehand. If it was just "oh he has something in his trunk - wonder what it is" it would have been a big surprise when he pulled it out.