Night after night, as the lights go down in the Neil Simon Theatre and musicians on guitar and flute and fiddle begin to play, a multiple Grammy-winning international star settles into a seat in a back row and drinks in anew all the Broadway sights and sounds. It's the closest that a guy named Sting will ever get to the life of an average Manhattan commuter. "I watch it every day," says the 63-year-old singer-songwriter, still in possession of the sleek build of a rock sensation half his age. "I'm fascinated by the process and the actors making this story and the songs their own. I'm fascinated by the audience and how they react. I sit way in the back in the dark, sort of a phantom, and l leave before the lights go up."