Voldemort was completely calm. Maybe he really didn’t feel anything: after all, this wasn’t all that unusual for him, apart from the unique circumstances of the loop. Harry froze, caught by the thought: he didn’t want to feel disappointed that his excitement wasn’t shared. So he just lay there, silent. His body was all hot, but Harry would have preferred to stay as cold as Voldemort — it was probably useful to know how to control your emotions like that.