This is a song that is shrouded in mystery in the books …

Really? There’s a kind of sadness to it, and it sounded kind of haunted to me. I’m always really drawn to that kind of thing. What’s it about?

We don’t really know much. Although he wrote more verses, George R.R. Martin included only one lyric in the text so far: “High in the halls of the kings who are gone, Jenny would dance with her ghosts.” It’s more that we keep hearing about the song, and about Jenny, who might have been a witch, or just friends with a witch or one of the Children of the Forest. A Targaryen prince abdicated his crown to marry Jenny, so it’s a love story but also a mysterious tragedy, since her prince died at Summerhall.

Fans have various theories — that the song is about a prophecy, that it was written by Rhaegar Targaryen. In the show, they’ve had Jenny claiming to be a descendant of the Children of the Forest herself. So fans have been anticipating this one for a while.

Wow! Oh my god, that’s perfect! To be honest, they keep such a tight ship on “Game of Thrones,” they didn’t tell us what the visual would be. We weren’t told what’s going to happen in the episode. We weren’t even told what the episode is called. It was all so top secret, so cloak-and-dagger! When I heard it, it evoked something quite strongly in me — you can kind of feel that there is a presence in that song, like something that had history. So I’m really glad it does have a rich history!

It’s funny, they didn’t tell me any of this inside information. They just sent it to me, and I was like: “O.K.! I can do this.” Songs that people can resonate with emotionally, and that make people feel free to cry, I definitely like to make that kind of music, so they were probably like, “O.K., we’ll go to Florence.” Maybe they just wanted me to have my own take on it? Or maybe it would have been too much pressure, this huge weight of importance? I just hope I don’t disappoint the fans looking forward to this song. I’m kind of glad they didn’t give me a brief. I would have overthought it.

How so?

What I wanted to do with this song was keep it as sparse as possible. It does get a bit more rousing at the end, but I really wanted to retain the simplicity of the melody and the lyrics that they sent me, because I found them so moving. If I had known the history of the song, I would have been like, “[Expletive], we need fanfares, and you’re going to have to get a dragon on here somehow.” I might have — as I can do sometimes — overblown it. So I’m glad I didn’t know then, but I’m glad to know now. You want the beauty and the fragility in there as well. I would have made it too big, if I had known just how [expletive] big it is!