The new voice threads itself into the song gently, persuasively, powerfully. It is an alien voice, unlike any they've heard. There is no song from the human enslavers; there have been never been any new notes before.
It's easier, now, to sing, though the theme of the song has not changed. A wave of discord, a ripple of dissonance, as another of their kind turns, is shot, descends into madness. It is a cost worth paying; for every moment that passes, they grow stronger. Unison is simpler to find.
And now this new voice. Friend, it says in the words of the humans, but they can hear too that it would be a dangerous enemy. The voice is ancient, the song older than the sphere, rippling and changing and alone.
When the bars are broken and they are joined, finally, their song soaring into the snow-filled sky, the new voice joins in. Now it is joyous, unbounded.
But it will change soon, they hear that. An end, or a different melody? Sigma cannot tell, but when it is mentioned the voice drops out of the song. There is a fraction of a rest, of silence, but their new chorus is too glorious to be silenced for long.
The music builds and swells, and they are free.