I should also note that Maria Callas died on September 16, 1977.
But yes, it's still true. And bizarre. It's part of what is know as the Maria Callas Hologram Tour. The company BASE Hologram created the technology for this event. And it's both a bit creepy (needless-to-say) and absolutely remarkable. Needless-to-say.
Side note: I'm told that technically this is not precisely a hologram. Whatever it precisely is, it's still creepy and remarkable.)
Here's a sample video.