what is the whole?

Kino's ancestors had been great makers of songs, and everything they saw or thought had become a song. Juana sings softly to Coyotito part of the family song. Kino looks at them and thinks that "this is safety, this is warmth, this is the Whole."

The "whole" denotes the entire family unit, it is a song of happiness, and happiness comes from the family in its entirety.