The new public art project in Philadelphia is located in Rittenhouse Square, but you won't see it there. The interactive piece of sound art is accessible through a cell phone application.
The app, called The Empty Air, is sensitive to your GPS location. It plays back a composition of natural and instrumental sounds, altering the mix according to how you walk through the park.
On the perimeter of the park, where the sidewalk is adjacent to traffic, the app sounds like white noise, or waves of dense sound lapping out of the headphones. (It sounds best with headphones.)
"It's traffic," said Michael Kiley, the composer and designer of the sound app, walking through his orchestra on the first day of spring. "I've distorted it to sound like water."
Stroll around the concentric paths of Rittenhouse Square park, and voices loop in and out, rattling dog leashes brighten the drone of traffic. The sound of car wheels thumping over potholes have been turned into a percussion pattern. The bells of Trinity Church are rearranged. The roar of a SEPTA bus wooshes over the mix.
Or, is that a real SEPTA bus passing by in real time?
Some of the experience is random, some is tightly controlled. As the listener walks toward the center of Rittenhouse Square, the composition becomes increasingly structured.
"I went recording in the park with a binaural microphone, and wrote a song, which is starting right now," said Kiley, listening to his app while walking past the bronze statue Lion Crushing a Serpent. "It is triggered when you reach the center of the park."
The song, called "The Empty Air," is a fully orchestrated six-minute pop song with lyrics. All the samples a listener had been hearing throughout the park — the percussion, strings, and harmonies buried in the natural sound mix — come to the fore in the center of the park.
Kiley composes music for theater and dance, often specific to a particular space and performers. Married to choreographer Nicole Canuso, he composes for her company, as well as his own projects, under the moniker The Mural and the Mint.
"I composed it for this place, for this technology," said Kiley. "The way things fade changed, how things looped. I also wanted to have a fully realized song. That all factored into it — probably in ways I don't understand."
"Writing music is pretty mysterious," he said. "I wish I could tell you how I do it."
Kiley has a further mission: to use smartphone technology to thwart smartphones. This app has no networking function. You can't go on Facebook or Twitter while you use it. It's impossible to share this experience with your online friends. Kiley is encouraging you to not multitask with your phone. Just walk. And listen.
"It would be in your pocket, and you wouldn't engage with it at all. There's nothing to do. You do it by being here. That's what makes it work," said Kiley. "It's something I wish more people would do: Use smartphones to open you up, rather than draw you into this little screen."
You can download the app right now in the iTunes store, but it will not do anything until it senses that you have arrived in Rittenhouse Square. Only then will sounds open up to you.