July 19, 2010 By Frank Scheck NY Post It was like watching Clark Kent turn into Superman. For the first half of his Broadway concert, Harry Connick Jr., wearing a dark suit and tie, dutifully performed the standards that brought him pop success more than two decades ago. Jazzily crooning to the accompaniment of a big band such songs as "The Way You Look Tonight," "Hey There," "All the Way" and, of course, "It Had To Be You" from the "When Harry Met Sally" soundtrack, he skillfully fulfilled the romantic demands of his swooning female fans. But it was after the intermission, when he re-emerged sans jacket and tie, that his true identity was revealed. Sitting at a newly appeared upright piano and pounding out boogie-woogie rhythms, he displayed a sheer joyfulness that revealed where his musical heart truly lies. That exuberance continued for the rest of the evening as he played the sort of New Orleans-style jazz that gets toes tapping and butts moving. He looked like he was particularly enjoying himself in his duets with the terrific trombonist Lucien Barbarin, a born ham whose brazen flirtation with a bodacious woman in the front row became a running gag. Connick also displayed a hugely appealing charm and self-deprecating dry humor, one point even making fun of his short-lived Broadway musical flop "Thou Shalt Not." ("I had to go to Costco to get a shelf for all those Tonys," he deadpanned.)