The speaker describes a quiet, private room and the sounds that move through it: rain on the roof, a crackling fire, piano chords, the hum of a machine. Each stanza starts with "Every" and gives one sound a job. The rain empties the air of noise and leaves space for thought. The fire carries warmth toward the listener's skin and, the poem suggests, toward something deeper inside them. The piano pushes out harsh tones and favors the resonant ones. The machine cleans away filth and the dullness of routine.
In the final stanza, the speaker gathers all of this together as "my world." The sounds fall, warm, end, eat and emphasize, and the speaker's "ruins" seem to be what they work on. The last line repeats the first stanza's "ambiance of thought," which gives the poem a circular shape, like a mind returning to where it started. The mood is calm, reflective and a little solitary. Sound here is not a distraction but a way of clearing, healing and thinking.