A nostalgic song would be a song that, when listened to, invokes a sense of nostalgia in the listener. It makes the listener reflect on their past, possibly making them sad, or leave them with a bittersweet feeling.Nostalgic songs are different for different people. For me, “Never Grow Up” by Taylor Swift is a pretty nostalgic song. I dunno why, I first listened to it like a month or so ago, but it makes me think of the past, so it qualifies.