The speaker treats silence as a close companion. In the first two stanzas it feels warm and helpful: it echoes their thoughts, makes worries and hopes clearer, and even plays a favourite melody made of old, lost memories. Silence here is a place to think and to remember, almost like a friend who listens without interrupting.
The tone shifts in the third stanza. Now silence is something the speaker wishes for, and it carries a harder edge. It will "drown" other people in guilt for not having appreciated the speaker enough. The poem suggests the speaker has felt overlooked, and silence becomes both a refuge and a quiet way of striking back.
The ending turns the idea around. Silence is what "they" will make and accept, and the last word, "quietly," is left hanging on its own. The mood is calm on the surface, but beneath it sits hurt, loneliness and a held-back resentment.