It takes him a moment to gather the words, and when he answers, it is clear that he is quoting someone.

"My lord father said that the world is made of music, because it was sung into existence. So when you hear a nice song, it reminds you of how the world looks when it is not broken."

He never really understood that one, but this strange sadness that has overcome his fairies and a lot of other people seems to him like at least their brains are broken a bit. So maybe a song can remind them of how their brains are when they were not broken, and help them to find those unbroken brains a bit.