So, Karyn's song is able to calm down people, and more interesting it also undoes Amon's power of Chaos. Karyn says it's an ancient song.
Karyn: It is an ancient song passed down from generations past... It is a song to sooth and calm our hearts.
Lufia DS says that the Sinistrals are the same gods as the "good gods" that are mentioned a few times in the game, which were also said to be the creator gods.
Since Amon is the Sinistral of Chaos, of the good gods he'd obviously the god of Order.
What if long ago, Amon (as the god of order) taught the elves a song to restore order just in case there would be a time of chaos?