The Charnel house had all those elements- great sound effects, mood, setting, eeriness, (and Roberta Maxwells voice), that make great Mystery Theater Episodes! 
I must comment here that many episodes seem to have "INSPIRED" others, I won't say copy. For Example, Charnel House may have "inspired" the author of SHELTER ISLAND novel. "No way Out" may have Inspired certain aspects of the TV Show LOST. "Life Blood" may have Greatly Inspired the writer of the new Movie EX MACHINA. And there are more that I'm sure others can come up with. Just sayin'....