Whoa!

Sometimes?! We are at the Christmas chorale and the choir lines up in the right and left aisle to sing the finale. The auditorium is dim. I glance right and do a double take. Did my eyes deceive me? Ok! I’m impressed. I’m puzzled. What is it? A speaker? Some device for hearing? What!? The internet says it can be done but give no comparable example. I would guess it is a wooden ring. Ok! To each his own.
Street photography. I got a shot. I never saw the guy on stage. I do not know if there is a matching disc on the other side.