Our memories keep us alive, indeed. Tupac Shakur performed on April 15 at Coachella, 15 years after he died of gunshot wounds in Las Vegas. His hologram, projected on stage, sang by itself before rapping alongside Snoop Dogg, performing "Come With Me," "Hail Mary" and "Gangsta Party" for fans.

While the world has seen holographic performances by Mariah Carey, Carrie Underwood and a 3D cartoon, this appears to be the first 3D, live rendering of a musical performance by a dead person. Tweets during the performance showed concertgoers were variously moved: "I think I might have cried when I saw Tupac," singer Katy Perry wrote. "Was completely freaked out by the Tupac hologram," tweeted @molly_knight.

Reports differ about what company created the spirit of Shakur for Coachella. Los Angeles radio station KROQ credited Digital Domain in Venice, Calif., while Gawker named U.K.-based Musion, a holographic projection company that brought Mariah Carey Christmas performances to five European cities simultaneously (and let Carey make instantaneous gown changes, punctuated by a burst of sparkles). The Verge added that a special effects company, MPC, made a video using live footage, wire-framing and CGI to feed into the holographic technology.

Musion's technology works by projecting images onto a specially developed foil, according to the company's website. Musion's technique doesn't produce true holograms, which are still in development in labs. Instead, the company takes advantage of a modern version of the Pepper's Ghost illusion, first used for ghost shows in the 1800s. It can make "infinitely variable" holographic images of variable sizes, according to the site.

In the future, will Musion and similar companies bring the likenesses of more of our beloved performers on stage, such as Alicia Keys, or even resurrect some bands, such as the Beatles?

Watch a fan’s video of the concert here:

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