The speaker describes a people whose whole lives are shaped by air-raid sirens, and he seems both astonished and unsettled by it. "Can you believe it?" sounds like a stunned aside to the reader. The poem never names the people or the place, so it stays open, and the title suggests the sirens also mark moments of mourning, when everyone stops and stands still.
The central image is the siren as music: a "monotone / That contains all tones." The sound rises from the earth, passes through the body, and tears the sky open, so frightening that actual bombs feel "anticlimax." Even children and the very old can read its "subtle nuances," as if fear were a language learned from birth. The closing question is the most chilling. Do people play the sirens, or do the sirens play them? The speaker leaves it unanswered, and the mood is tense, eerie, and quietly sorrowful, as if routine and helplessness had become the same thing.