The Phantom Diaries

At my school, there's an old legend about Clarence. He's the auditorium's ghost. He's not very nice. You sit in his chair to the side, you mess something up in the next show. He stays there, messing around and being lonesome. I've been reading to him daily, whenever I have summer school. I've never been scared of him, until my friend comes in and sees him. Who... or what... am I reading to?