I'm still not sure we mean the same thing. What I meant is that the song goes on repeating itself like before, but the sound editor slowly turns down the volume. Say, like any Madonna song from the eighties, or this classic from Cindy Lauper:

the voice fades out to a whisper

I would say: the voice gets lighter, ends, and then there is a whisper.

_{*Lunatic*, n.
One whose delusions are out of fashion.}