We have a neighbor behind us and one house over that has an old beagle. And they leave it outside a lot more than it wants to be outside. So you get that deep, long, "hound-dog" howl/bark thing... For hours!
I remember this tiger once that was concerned super nice (for a tiger I guess) to its owners until one day is snapped and almost killed the guy. OK, over exaggerated comparison... In reading about animal psychology (fun class in college), I remember that it kept saying that instinct is VERY strong in all animals, and even if an animal is trained properly, if some unusual variable enters the mix, the animal can, and often does, resort back to instinct over training. So wanting to go outside and mark a larger territory is a natural instinct in the dog I saw. It could be trained not to do so, but may still decide to ignore the training should another dog come into the picture or something. It just wants to prove that it was there first and that it "owns" the place.
