A Symphonia is a rare device from the Day Court.
It's described as a silver ball the size of a chicken egg, round save for one flattened area so it might be set upon a surface and not roll. Tapping the top, makes music play. The device can trap music within itself, and play it back.
The device was originally invented to help compose music, but it never caught on, for unknown reasons.
- A Court of Silver Flames: Chapter 58