The nature of bond between these two songs (Sound of Wild and Rabbit Hole) lies in the idea of human contemplation about the darkness within themselves. Sound of Wild talks about us, calling into our internal primal animal, while Rabbit Hole talks about one of the phases that we have to go through during that process, which is falling into depression. Either depression or the exploration of the darkness, whichever comes first, it depends on each person. The obvious is that those things are sure going to happen. It is inevitable.