On the roof, as it were one on each side of him, were two toad-like creatures which seemed constantly to be changing shape and appearance, and from whom emanated, by some means I could not distinguish, a ghastly ululation, a piping which was matched only by the shrill choir of the frogs, now risen to an truly cacophonous height.
~ H.P. Lovecraft & August Derleth , The Lurker At the Threshold