Instrument
Chordeograph 1
Deconstruction of the piano
Since the invention of the prepared piano by the American composer John Cage, it has been a matter of course for musicians and composers to enrich piano playing through actions inside the instrument. For years the composer and performer Gero Koenig has been systematically rethinking these techniques. This lead to the development of the Chordeograph, a stringed instrument which started out as a modified piano, but which has evolved into a completely new instrument. The Chordeograph’s unique sound world came about through drastic modifications and proprietary developments, going beyond the construction and static tonal system of the piano.
Chordeograph 2
New design with extended sound spectrum
Chordeograph 2 was developed in order to expand the range of application and the sound spectrum of existing string instruments.
It was built in two versions: the first in 2008–2009, the second in 2010–2012. String calculation as well as bridge and nut construction had to be completely redesigned in order to achieve a continuous transformation from broadband noise to unison by purely acoustic means.
In the first version, 32 line laser modules projected graphic scores onto the strings as a time-bound sequence of guide beam constellations. The information of the score was thus fully integrated into the instrument. However, the modules proved too inflexible to adjust and offered no possibility of linking them to position tracking and analysis of the actual playing. They were abandoned in the second version.
Contributors
Gero Koenig (construction, acoustic assembly and string calculation), Alexander Bittmann (instrument construction), Peter Kelemen (bass string manufacture), Ulrich Dernbach and Ernst Grigo, Metall & Mehr (metal work), Dr. Dr. Arnold Esper (control hardware, laser interface, 2008–2009), Jonas Förster, ICEM Essen (programming, laser interface, 2008–2009), Bernd Wendt (design)
Chordeograph 3
Extended Resonance Body – An Intermediate Step
Chordeograph 3, begun in September 2020 as a new construction, proved to be an intermediate step: 185 additional resonance strings, strung across the back of the body, were intended to open up higher resonances as individual tones in hybrid-acoustic quality. The sonic possibilities, however, do not exceed those of Chordeograph 2. From this finding came the approach that defines Chordeograph 4 AR: instead of further mechanical resonators, an integrated audio analysis combining a pickup array, high-resolution frequency analysis over time, and laser-based position tracking – and, building on this, the feedback onto the strings via the transducer.
Funded by the Ministry of Culture and Science of the State of North Rhine-Westphalia.
Chordeograph 4 AR
Extended hybrid acoustics and web-based concert setting
The aim of the development is to interactively explore the unrivalled wealth of complex mechanical vibrations of the strings, in order to make sound transformations from the electronic and computer music fields a more tangible concert experience.
Chordeograph 4 AR, short C4AR, builds on the resonance body of Chordeograph 2. The acoustic body from 2013 was extended in 2017 for Chordeograph AR with a transducer system for touchless playing, presented in this form at ZKM Karlsruhe in 2018. C4AR adds a pickup array and laser-based position tracking.
Augmented Analysis
The current development integrates laser-based tracking of sound generating tools like sliders, and detailed analysis of string sound properties through an array of pickups. This enables deeper insight into sound generation and allows for physical interaction with string vibrations in real time.
Through targeted excitation of overtones – including those not present in the mechanically produced sound – resonance regions of the strings (formants) can be brought out from the overall sound. The transducer excites the string and at the same time radiates through the resonance body – it is from this interlocking that the instrument's hybrid acoustics arise.
Augmented Reality
Through digital data transfer and body tracking, both on-site and remote audiences are invited to become part of the concert experience. Only control data is transmitted over the network; the sound is produced at the instrument. Participants can engage with a wide spectrum of sound modulations using state-of-the-art visualization techniques and intuitive gesture-based controls.
Development
since 2017 ARScore: control software with multi-bot structure
2017 Transducer system for touchless playing, Chordeograph AR
2022 Remote Feedbacks: tests with individual electromagnetic pickups, network-based control of the feedback from remote locations
2022–2023 Laser-based position tracking of the sliders
2023–2024 Multithreaded audio engine in C++ for multi-channel processing
2024 3D interface with TH Köln
2025 New studio, further development of pickup array and transducer feedback system
Oct–Dec 2026 Extended AR interface for interactive performances
Contributors
Gero Koenig (concept, instrument and software development), Alexander Bittmann (instrument construction), Ulf Schaedla (electromagnetic pickup, 2012–2014), Thomas Perizonius and Willi Blum (pickup system), Jan Wilczek (framework of the audio engine in C++), Maximilian Timm (AR interfaces and web connectivity), in cooperation with the Institute for Media and Photo Technology at the Technical University of Cologne and storyLab kiU at Dortmund University of Applied Sciences and Arts
Funding
Funded by the Ministry of Culture and Science of the State of North Rhine-Westphalia, by Musikfonds e.V. and by GEMA.