It happened spontaneously at a concert in Boston’s Symphony Hall last Sunday. After a beat, as Ronan’s awe-filled “Wow!” echoed throughout the hall, the audience burst into laughter and cheers. So charmed were the Handel and Haydn Society by the child’s exclamation that they asked the public to help find him, hoping to reward the sweet sentiment with a trip to meet the artistic director. – WGBH