When Dre came out, that moment of the show, I became a fan. I was no longer DJing. At that moment when Dre came out, it was like, “Oooooh.” He was five feet from me, he came out the floor. He was rising. It was like watching a video. It was the theatrics of a video. When he came out and did his Dre bop, it was like he never left. When Em said, “You see what I do for you, Detroit”, I knew Em was really comfortable.
Source - http://nahright.com/news/2010/09/05/video-the-alchemist-speaks-on-dr-dres-appearance-at-eminem-jay-z-show/