“Stage Fright” starts out as a funny musical mashup — “Glee” meets“Friday the 13th” — but winds up indulging slasher-flick clichés instead of spoofing them.

An appealing Allie MacDonald plays a cook at a summer theater camp for kids who tries out for a “Phantom of the Opera”-like stage show in order to conquer her phobia resulting from the grisly demise of her actress mother (Minnie Driver) at the hands of a masked figure in her dressing room.

Director Jerome Sable, who along with Eli Batalion wrote the songs, should have stayed with the path established by a bright comic opening number mocking theater nerds. Instead, Sable’s gruesome film is as numbing as the average horror movie, albeit one occasionally interrupted by singing.