As far as the question posed by Draheim goes, I tend to feel that they probably couldn't hear it. When music plays in game, we tend not to recognize it ICly because it's just coming out of nowhere. It'd be weird if you heard a chocobo song pop up whenever you mounted your chocobo.
That said, I think you can maybe say that they can hear the song in a metaphorical sense. Like hearing the noises from the vibrations as Dalamud tears through Hydaelyn's atmosphere, like answers to the planet's call of distress, and thinking of it as a sort of song made by nature? I don't know. There's no reason given by the lore, apart from the nod given by Jainelette's harp playing, to think that Dalamud Answers is anything but a song meant only for the player to get in touch with the atmosphere of the current area in the current situation.
Like many things, I think it's not important enough to say it should be one way or the other.
That said, I think you can maybe say that they can hear the song in a metaphorical sense. Like hearing the noises from the vibrations as Dalamud tears through Hydaelyn's atmosphere, like answers to the planet's call of distress, and thinking of it as a sort of song made by nature? I don't know. There's no reason given by the lore, apart from the nod given by Jainelette's harp playing, to think that Dalamud Answers is anything but a song meant only for the player to get in touch with the atmosphere of the current area in the current situation.
Like many things, I think it's not important enough to say it should be one way or the other.
