The tone of a work of literature can be defined as the attitude that the author takes on the them, a character or an object within that work of literature. When we consider the overwhelming message of this excellent poem, which regards the way that men view and construct an idealised view of womanhood and femininity that springs from their own imagination and has nothing to do with the way that women themselves view their position and gender in society, we can describe the tone as sad and sombre, as the speaker reflects upon this state of affairs in her culture and society. Note how this wistful and sombre mood is created in the last three lines of the poem:
Not wan with waiting, not with sorrow dim;
Not as she is; but was when hope shone bright;
Not as she is, but as she fills his dream.
The way that the female subject of this poem is described clearly highlights the negative impact of this idealisation upon her. She is described as a mere shadow of her former self, "when hope shone bright." She now only has existence, not in her actual appearance (and note how the four words "Not as she is" are repeated to emphasise this) but only as "she fills his dream." She is interpreted and portrayed from his perspective, rather than having any reality or life of her own. Thus the sombre tone of the poem is established.