I was just thinking... what if she projects the interludes the way Miku Hatsune is projected? What if she was searching for ways to project 2D images to make them look 3D and that's how she came across Hatsune?

Imagine hologram-esque interludes of her on the stage.
This sounds plausible to me because the main screen is behind the castle and projecting interludes onto that wouldn't make sense because you wouldn't be able to see them that well.