Re: What happens when the drumming stops?
I don't think a joke has to be funny to everyone. I didn't find it very funny either, but there were two things that made it clearly a joke. It was supposed to be funny, and it followed a very predictable template. The premise makes you believe that the meaning of the drumming ending is something seriously problematic, but it turns out to be something very benign. That's a very common structure of jokes, the creation of suspense and a disproportionately small outcome of the suspense. It's used in humor all the time, some much funnier than this.
Of course, nothing makes an attempted joke less funny than breaking it down and discussing the tropes and structures of comedy, but I don't think something stops being a joke just because you don't find it funny. In fact, I'd go as far as to say that, even if nobody at all found it funny, as long as the teller intended it to be funny, it can still be termed a joke. It would just be a joke that failed utterly.