Composer Ellen Reid, a recent Pulitzer winner for her opera Prism, has created a site-specific score for exploring Central Park. Soundwalk is a free-to-download app that features Reid's work as recorded by New York Philharmonic musicians, members of the Young People's Chorus of New York and a couple of other ensembles. The soundscape, which features hidden surprises, is meant to enhance the park's landscape and attractions. The route you choose dictates what music you hear.