Answer :
Poe is a very complex writer who loves to experiment and the poem "The Raven" is a valid proof of Poe's understanding of symbols in universal literature and his wish to explore and have control upon words and rhythm. The repetition of the word 'nevermore' comes to amplify the elegy that mourns the loss of the beloved Lenore. The effects the long vowels produce are shivering the readers' heart. Lord Byron himself experimented the play upon sounds in his poems before. Raven is the metamorphosis of a tragic love, a favourite symbol of death in many pieces of literature from ancient times. The visual contrast of a white bust like a ghost to the dark black raven in a "bleak" December, like in Dickens's "Bleak House", reinforce the tone of mourning a dear person.
In point of rhyme composition, the poem is fully based on Elisabeth Barretts' sophisticated rhythm and rhyme of "Lady's Geraldine Courtship" poem. The rhyme scheme is ABCBBB. The heavy use of alliteration, "doubting dreamy dreams..." plays huge role in the musicality of this beautiful narrative poem of 18 stanzas in which every B line rhymes with the obsessive "nevermore".