A cello is strummed, a clarinet caressed, the shrill high notes of an oboe carry, and a trombone tempers to silence - all by way of a smartphone. Visitors to Berlin's celebrated Holocaust Memorial can now wave their smartphones over a QR-Code to download a virtual concert - a recording of German composer Harald Weiss' much lauded 2008 work, "Vor dem Verstummen" (Before the Silencing). Weiss wrote the piece, marked by technical refinement and oppressive sounds, for a performance in the middle of the memorial.

"We wanted a new, so to say, acoustics look at the space," says Daniel-Jan Girl, the project's initiator and app developer.

A one-off concert

Twenty-four wind and string musicians from the Berlin Chamber Orchestra were positioned throughout the 2,711 cement blocks. By way of a miniature monitor, the musicians were connected with their conductor and performed this unique musical work before a crowd of 3,000. Each audience member experienced the performance differently. Depending on where they stood, the sound of certain instruments was softer or louder - a metaphor for separation of individuals during the Holocaust.

Due to the cost and effort involve, the concert only took place once. But for Girl, the youngest member of the organization created to secure financial support for the Holocaust Memorial, once was not enough. He wanted the site's future visitors to experience the music as well.

An app makes it possible

After quite some time thinking about the nature of remembrance culture, and how it can be updated for the 21st century, Girl found the answer he was looking for in his pocket.

What's in there is in easy reach for most of his generation: a smartphone. "We are now in the second generation [after the Holocaust]. For us the question is, how do you deal with historical responsibility? When you think about the Holocaust, you feel this crushing weight," says Girl. "With music and technology we've tried to find a universal approach to the subject."

With the aid of donations and crowdfunding, Girl was able to gather enough money to develop an app that would allow the recording of the concert to be presented in a way that is faithful to its original performance.

Using the smartphone's GPS, the app locates the visitor's exact coordinates within the memorial and plays the sounds of only those instruments that he or she would have been able to hear from that standpoint on the night of the original performance. As the visitor walks toward where the cellist was playing and away from the trumpeter, for example, the intensity of the trumpet fades and the intensity of the cello picks up.

Prominent support

German actress Iris Berben, who has been involved with the Holocaust memorial for decades, helped lay the first of 23 QR-labeled stones throughout the memorial. They resemble the Stolpertsteine, or stumbling stones, that are scattered throughout cities across Germany, marking the spot where individuals murdered by the Nazis had once lived.

Berben was inspired by the project as soon as she heard about it. "We must forge new paths through our remembrance culture," she says. "And this new technology is one way we can ensure remembrance is preserved."

Currently, the app is only available for iPhones. An Android version is in the works. A version of the performance can be heard under the following link: www.virtuelleskonzert.com.