Why does goding compare the choir to a creature as they approach the other boys when Ralph sounds the horn? What could this foreshadow about the choir? Explain.

Is this the passage you're referring to in your question?

Then the creature stepped from mirage onto clear sand, and they saw that the darkness was not all shadow but mostly clothing. The creature was a party of boys, marching approximately in step in two parallel lines and dressed in strangely eccentric clothing. Shorts, shirts, and different garments they carried in their hands; but each boy wore a square black cap with a silver badge on it. Their bodies, from throat to ankle, were hidden by black cloaks which bore a long silver cross on the left breast and each neck was finished off with a ham-bone frill.