In our time, aside from death, we have little personal experience of what it means to say farewell completely and forever, a final farewell. We are never separated by more than a phone call or a plane ride. This was not true before in history, much less prehistory, when a journey of much distance was frequently an absolute separation for the rest of life. 

And it will not be true in the future, either, because we live in a universe with a ridiculously low speed limit (the speed of light). Just to communicate via geosynchronous satellite introduces a delay of a quarter of a second. When we have settlements on the Moon, the delay will be over a second, making coversation difficult. On Mars, never less than four minutes. And when we have spread to even the nearest stars the delay will be years. Conversation and real interaction will give way to outdated reports, and we, in whatever form we may then take, will learn again what our ancestors knew, what it means to say a final farewell. (It is interesting that for AIs, because they think much faster than we do relative to the speed of light, the distance over which real interactivity is possible is much shorter than it is for us: about ten million times shorter.)

It is, I admit, odd to compose a song of final farewell at the unique point in time in which we generally lack the personal experience to fully understand what the song means. But that makes it an interesting challenge. The domain of a poet is the whole of life, not just their own.