Just how do two legends as Jay Z and Justin Timberlake are quite reasonably billing themselves on their first tour, Legends of the Summer, together share a stage? In at least one memorable moment at New York City's Yankee Stadium, their first American stop on a jaunt crisscrossing the country through Aug. 16, it was with the merry give-and-take of a vaudeville routine: As Jay Z expertly ran through a stadium-rattling rendition of ''99 Problems,'' Timberlake stepped up to voice the nasally cop who condescends to a legally savvy Hova. (''Well, aren't you as sharp as a tack!'')
The cheery, elastic Timberlake is an excellently goofy foil to Jay's forbidding cool if these two were superheroes instead of mere legends, Timberlake would be Robin to Jay Z's Batman. The two worked continuously as a team, kicking off the set with ''Holy Grail'' (their collaboration from Jay Z's new Magna Carta...Holy Grail, his 13th straight No. 1), encoring with ''Suit & Tie'' (from Justin's The 20/20 Experience, currently the best-selling album of the year), and joining each other on stage many times in between, including for a cute two-step during Jay's ''Excuse Me Miss'' and a segue into the classic Aerosmith/Run DMC mash-up ''Walk This Way.''
But as much as the two had to celebrate together, they didn't get much chemistry bubbling beyond their ''99 Problems'' role-play. (It was, to be fair, a charisma-sapping 95 degrees out.) Jay Z, in a backward Nets snapback, paced the stage with a studied nonchalance, pouring all his energy into his explosive, bull's-eye-accurate rhymes, while Timberlake swept from piano to guitar to mic stand with the loose-limbed gait of an unusually graceful 8-year-old, injecting slightly hammy musical-theater verve into the hooks of songs like ''Heart of the City.'' What the singer-actor and rapper-CEO brought were hits so, so many hits. Roughly three dozen, from ''Cry Me a River'' to ''Mirrors,'' ''Hard Knock Life'' to ''Ni**as in Paris'' (and only a few of the mostly mediocre tracks from their respective new albums, although Jay Z's ''Tom Ford'' sounded fantastic like a fashion-designer-inspired earthquake). They also invited a couple friends: A grinning Timbaland joined in on ''SexyBack,'' and Alicia Keys won some of the night's loudest cheers when she emerged in electric blue leggings (her superhero alter ego? Catwoman, definitely) to lead the chorus of ''Empire State of Mind.''
All these dynamic shifts might've derailed the show were it not for the tireless energy of the four backup singers and 14-piece band manning everything from cowbell to tuba.
But of course, it all came down to Justin and Jay, who, in the end, wore their megastardom lightly: For the encore, they donned tux jackets and took up flutes of champagne as if to say, ''What a gas!'' When Jay Z dedicated the night's last song, ''Young Forever,'' to Trayvon Martin, the two stars ceded the spotlight to a stadium full of lit-up phones props no weightier than the champagne flutes, but charged with emotion. B+