The Philadelphia Orchestra has commissioned a new piece of music, to feature the voice of you. Everybody in Philadelphia is invited to download a mobile app to his or her phone and use it to record anything they want, then upload it to a server. That sound will be used to make a new symphonic composition to be performed next spring. Composer Tod Machover, who heads the Opera of the Future research group at the MIT Media Lab, calls his crowd-sourced pieces "City Symphonies."