It took a few songs to get used to the headset microphone. That's not a look one associates with Sting, but the rock star must not have wanted any microphone stands limiting his mobility Monday on the opening night of a sold-out, two-show Heinz Hall engagement with the Grammy Award-garnering Pittsburgh Symphony Orchestra. Free to roam, Sting glided around the stage, sporting a slate-gray jacket atop a tight, sheer shirt, showing off a still-enviable physique, at age 71...