There's actually software that could make "new" samples of his voice just by combining several of his songs, Vocaloid style.
It's rendered in 2D, and it's not a stock footage, according to the 'creators'
In all technicality it is
not a hologram, as a hologram is a 3D produced image; this model is a 2D custom made by a method of using old footage and CGI; it is mostly CGI based (Computer Generated Image). While it is not exactly known how the 'authentic voice' of 2pac screaming out Coachella (conspiracys already in the rise) was exactly produced, however most of the audio is again mixed of actual footage, demo recordings, CD recordings. The only thing with the Coachella, is that pac never preformed at that venue, so no audio exists of him screaming that out
2 Major coonsipracys have arrised (on top of the hes alive)
1. He
was is alive and present, watching his hologram from the crowd.
2. He is alive, and helped Dr. Dre with the creation of the hologram.
I was able to find these (original credits to New Scientist)

The slant in the middle is a mirror btw.