(or "Perfect Pitch")
When looking at an anthology series like 'The House of Mystery', we can strip away a lot of the things we've been discussing in this series. Aside from the framing sequences, there are few if any recurring characters or settings, there's no real "central concept", and really, all that's important in the stories themselves is the tone of horror mixed with gallows humor.
Which makes the tone all the more vital. In fact, in any anthology series, keeping a consistent tone is the most important difference between a series that keeps going and one that gets cancelled. After all, when a reader picks up a Spider-Man or Batman series, they have a general idea of what to expect. A Spider-Man comic that's "off-beat" will still feature Spider-Man, and he stays consistent even when the story is out of his usual tone. (This is why Spider-Man gets into so many crossovers--he can be counted on to provide the reaction of a normal guy, even in weird cosmic situations.) But with an anthology series, there's nothing for the reader to expect. Creative teams vary from issue to issue and indeed story to story, protagonists don't always stick around for long (especially in a horror anthology, where "don't always" can be replaced by "rarely"), and settings vary widely. That consistent tone is all that readers can really expect to get when they pick up a new issue.
The framing sequences help a lot to set this tone, which is why "apart from the framing sequence" is a bit of a cheat. By establishing a narrator with a strong personality that fits the tone of the series (Cain, the narrator of 'House of Mystery', is a wonderfully cynical heel with a world-weary eye for human nature), the series has a stronger narrative "spine" that connects together the stories in a shared "world". The House itself provides a convenient narrative hook for writers, which isn't necessary but can certainly come in handy. And a few recurring features, such as the "Page 13" gags and some wonderfully black comedy pieces by Sergio Aragones, can help create a sense of familiarity that helps readers plunge into stories that have to establish their characters and settings from scratch each time.
Every comic tries to establish a sensibility that helps both readers and writers know what to expect when the next issue comes along; when dealing with the blank slate that each issue of an anthology provides, this isn't a straitjacket, it's a life-vest.