Though the genre has been around for only 20 years, mumblecore films have common signifiers. They’re low-budget, mostly single-location films with few characters and naturalistic dialogue.  Chris and Jay Duplass made a cottage industry of these films (my personal favorite is “You Sister’s Sister”) before each of them branched out into more “mainstream” projects, including horror.  Chris made the “Creep” films and now Jay stars in “Ghostwritten,” a ghost story that still keeps one foot planted firmly in the mumblecore world.