His videos caught the eye of international names like jazz-pop singer Laufey and American media personality Paris Hilton. In quiet pockets of Woodlands Crescent Park on a Thursday evening, those out for an evening walk might chance upon an unassuming elderly man running through vocal scales armed with a pitch app glowing from his mobile phone.    The 75-year-old often walks back and forth on the viewing deck, his voice steady, unhurried and resonant, floating across the park.  Despite some