"We’ve done things together," the Detroit rapper told interviewers when announcing his upcoming shows with Jay-Z. "But I’m not sure we’ve ever done anything this big."

With the superstar duo set to stage a massive home-and-home series — a pair of Comerica Park shows this week followed by two at Yankee Stadium — the superlatives are coming thick and fast from those close to the event. The biggest North American concerts this year, says one Comerica Park executive. The heaviest ticket demand one Live Nation honcho has ever experienced. A "once-in-a-lifetime production" for an industry veteran who has staged Super Bowl halftime shows.

There’s historical significance too. The sold-out dates aren’t just testament to the enduring power of Em and Jay-Z, two of the world’s biggest music acts — they also mark a milestone for hip-hop itself.

"They’re putting hip-hop on the same playing field as anything else," says L.A. hip-hop journalist Scott Sterling, citing rock’s storied history of concert spectacle. "If I’m a 15-year-old who’s getting into this music, it makes anything possible."

Turning Detroit into the center of the music world for two days has been months in the making.

"Marshall and Jay had the idea," says Live Nation’s Rick Franks, "and from there they ran with it."

Plans were shepherded via Jay-Z’s relationship with Live Nation — the pioneering "360 deal" that gives the company a stake in his tours, recordings and publishing.

First on the list: nailing down a window that fit the baseball schedule, while accommodating the show’s unique needs as a one-off event rather than a full-length tour.

"The production is very, very complicated, a lot of moving parts, because it’s only the four shows," says production director Dan Parise.

Work began several weeks before the May announcement. World-renowned lighting and scene designers were enlisted, and at Live Nation’s New York office, specialists dove into 15-hour days, crafting stage renderings and configuring logistics.