QUOTE
IT WAS decided that should a mirror ever actually speak, there would emerge from its silvered surface a sepulchral, masculine voice. For weeks, voices were recorded in boxes, through sheets, before sounding boards. At last a sound technician hit upon the idea of building a square box with old drumheads stretched taut over five sides, leaving an opening in the sixth. Through that opening an actor placed his head, spoke the prescribed lines into a nearby mike, and became the talking mirror.
Interesting site. Will go back and read more later.