Caleb's experience
Source chapters: Chapter 4Caleb is certain he has never heard it, yet it feels as familiar as breathing and keeps pressing to be sung instead of the family verse. He continues singing correctly while the separate melody persists underneath, bringing a feeling of belonging and a comparison with arriving at a familiar house. He considers that someone, perhaps Sib, once hummed it to him, but knows this thought comforts him rather than establishes how the song reached him.
When he compares it against his knowledge of harbour songs, none corresponds, and he cannot associate it with any work or weather he has known.