Pop-Up Pianos was a 2011 initiative of the nonprofit arts group Sing for Hope, for which 88 grand and upright pianos--one for each key on the keyboard--were decorated by artists ranging from Isaac Mizrahi and Olek to public school children. These pianos were then placed outdoors in all five of New York’s boroughs for a period of two weeks, in locations both iconic and unexpected, creating the world's largest street piano installation to date. Two million New Yorkers—stockbrokers, students, nannies, seniors—delighted in the pianos under the Brooklyn Bridge, on the Coney Island boardwalk, nestled among skyscrapers in Midtown, and in full view of the Statue of Liberty. Photographer Lekha Singh traveled through all five boroughs to document the public revelry and euphoria. Essays by Sing for Hope Co-Founders Monica Yunus and Camille Zamora.