Our mission in this project was nothing less then to create a musical instrument from scratch. So we started out to explore the capabilities of PureData, a visual programming language for signal processing. PureData is somewhat like the open source grandfather of Max, so in a nutshell it allows you to create your own synthesizer, audio effect rack, drumcomputer or whatever else you can come up with that can be built with oscillators, filters and other basic building blocks of the DSP domain.
Since real world instruments tend to have a body that creates a specific resonance and dynamics that help to form a distinct sound, we decided to use the physical modelling library pmpd to give our instrument a character. This libaray allowed us to simulate the oscillation of a string. So we had the simulated string on the DSP side, but we needed a matching hardware interface.
On the hardware side we used an Arduino Uno board to connect the real world to our PureData project. A conductive rubber band was the perfect fit for our simulated string instrument. The resistance of the band gets higher once it is stretched. By pulling the band we triggered sounds to be played. Once the pressure was released, the resistance of the band slowly went back to normal and the sound of our virtual string faded out smoothly.
For our final instrument we put six rubber bands on a tripod and arranged them with tennis balls so we could play the instrument and provide additional visual feedback for the audience. In the course of the event „Carving The Sound Space“ in the University of Technology Vienna the instrument was presented and played live.