"A poem may not be 'dead' in itself, but the song minus the tune is dead as a song, surely?"
Agaain nobody is talking in the extremes - dead or not dead - it becomes a matter of emphasis
You can present a songs as a beautiful (or beautifully sung) music that happens to have words, as most opera has to be to those who don't understand the languages they are sung in
It is fairly common for a song to be 'over-accompanied or over-ornamented
Once that happens it becomes a piece of music with words, rather than a narrative
That was not what the old crowd did (not in Briain and Ireland anyway - Americam traditions developed differently
Jim