Nothing can happen that God does not want or intend, although it doesn't have to be deterministic. One could see it as the introduction of a dramatic theme right at the beginning, replacing the previous serenity and really getting the song going. But we don't understand it, of course. We must have faith, faith in God, faith in ourselves, so our voices are strong and beautiful, regardless of what we sing. The dark and apparently disharmonious voices are part of the whole, which we cannot hear in our limited state.
Faith is terribly important.
Most beings lack faith, and just plod along without realising their inherent greatness or the presence of God around them. God does not need faith per se, since It is the basis for all that exists, but faith shapes our perceptions of God and our songs. As long as they have faith in one aspect of God, they are on the right path. The details doesn't matter. Even some Satanists are true to God, since they worship Its dark side.