All aboard the Downtown Train! Rod Stewart hopped the stage at New York’s downtown Tribeca Rooftop to croon American classics at the gala launch of his latest album It Had to be You: The Great American Songbook. All-white-clad and forever-young-looking Stewart tuned standards like “These Foolish Things” and “The Way You Look Tonight” in his inimitable style, while A-listeners Alicia Keys, Joey Fatone, and Ron Perelman and wife Ellen Barkin applauded the swiveling, gyrating icon. As host Clive Davis—Arista Records’ founder and now J Records’ CEO—put it, Rod is simply “one of the greatest voices in contemporary music.” Davis should know—he discovered Keys, Whitney Houston, Busta Rhymes, Luther Vandross, and Carlos Santana, among dozens of other music legends. Taking in the show, guests nibbled on specially prepared sushi, dim sum, and Peking duck on the posh rooftop. Maggie May would have been proud …