“Though classical composers aren’t supposed to get any love until they’re old (or dead), the 27-year-old is already collecting commissions at a graybeard’s pace. … In the last year, Muhly composed the soundtrack to The Reader, issued the dizzyingly fine disc Mothertongue, had an evening of works presented by Lincoln Center” and worked on an opera commissioned by the Met. His biggest potential problem might be overexposure.