Why was the overflow crowd at Wolf Trap on Wednesday night absolutely wild about Harry Connick Jr.? Sex appeal certainly had something to do with it. Just ask the folks in the front rows who were peering through binoculars. "My goodness," said the New Orleans-bred pianist and crooner when he spotted a peeping fan. "Could you make me feel any more self-conscious?"

Of course the music also played a big role in generating the waves of ovations that punctuated the humid night air, since Connick and his big band often evoke pop's past with a mixture of old-fashioned lyricism and brassy bravado. But the prime reason Connick wins over crowds so easily can be summed up in one word: showmanship. Whether putting himself down in disarming fashion--"The drunker you get, the better I sound," he told a pair of well-lubricated fans--or briefly climbing atop his piano so picnickers out on the lawn could see him dancing something that resembled a butt-shaking, not-so-Funky Chicken, Connick always seemed to know precisely how to please his audience.

Though drenched with perspiration, he obviously got a kick out of the concert as well. When he wasn't happily and capably indulging his passion for singing Cole Porter tunes--the evening was laced with familiar and not-so-familiar Porter gems--he was often at the keyboard, playing infectiously syncopated New Orleans piano. He took particular delight, though, in showcasing his impressive big band, which includes such gifted jazz musicians as saxophonists Gerry Weldon and Jon Gordon and trumpeter Leroy Jones. Not surprisingly, the biggest crowd-pleaser was Connick's inevitable reprise of "It Had to Be You," though a bad case of the giggles prevented him from getting all the words out. "I hope I haven't ruined your wedding song," he told the crowd before letting his band redeem the tune.

CAPTION: Crooner Harry Connick Jr.