In the greenest of our valleys how does poe use a sound in the excerpt

The main sound device is rhyme.  Also, note that the accent in the verb "tenanted" is placed on the last syllable, which makes it rhime with "head". The same is done with the word "musically", in order to make it rhyme with "valley". A syllable is added to the usual pronunciation of the past participle "tuned" by placing a grave accent on it, "tunèd", for the sake of the rhythm in that verse.

the answer is something i don't know

normally working animals are domesticated and ruled by a master, a domesticator (tamer), to perform basic and important functions on a farm, for example. the value used in this context is animal labor in exchange for food. it is not so much a contrast to the story told by napoleon and the pigs, since the animals of that particular farm also performed functions on the farm through domestication. the only thing is that in this case, who rules them is a pig, also an animal, but very respected, to whom the other animals lent him submission. that's about a strong relationship of dependency between animal and owner.