What does Cassian give Nesta for Winter Solstice?

Cassian gives Nesta a gift for Winter Solstice. When she opens the box with her present, she finds a silver ball the size of a chicken egg. One area is flattened so it can set on a surface and not roll. Cassian tells her to tap the top. She does so, and music fills the room. Cassian tells her it is a Symphonica. It can trap music and play it back for you. He had the musicians at the Hewn City play the music from the ball and some of their favorites. Then he went to her favorite taverns and had those musicians play.