In chapter6 Why had the song of the family replaced the song of the pearl in kino's head?

In the beginning of the chapter6, "the song of the pearl was triumphant in kino's head, and the quiet melody of the family underlay it..." and near the end, " kino's own music was in his head, the music of the enemy, low and pulsing, nearly asleep. but the song of the family had become fierce and sharp and feline as the snarl of a puma."

Why had the song of the family replaced the song of the pearl in kino's head?