The "ghost's song" referenced in 3373's second segment — "that impossible resonance of willed self-sacrifice" — is a callback to an earlier Echoes event. Without the ghost's song, Rhys would have remained a hunter, categorizing and containing the four consciousnesses. The song "irrevocably altered him" by demonstrating a choice outside the System's calculus: self-sacrifice is economically irrational, strategically unsound, and logically unmodelable — yet it happened. The song broke the System's framework not by disproving it but by transcending it. The echo of that song is what allows Rhys to become a witness rather than a hunter.