Hatsune Miku is also a projection, not a hologram. But I think it's "further" than you think, because every single song at the concert is created by a musician or team that releases the song online for free. The extremely popular ones are put into the concert, as a way of saying thanks by the company who makes the voice synthesizing software to the fans.
Miku is likely part of my dissertation; extremely outdated research page here: http://alexleavitt.com/vocaloid