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water organ

Aura calculata is a water organ sculpture based on 18 acrylic glas pipes aranged in a circle. A water reservoir is placed in a central column. Two walves on the bottom of the pipes control the water to flow in and out. At the beginning the inflow valves of all pipes are opened. Water flows in and the level ballances with the level in the reservoir and the other pipes. When the first air starts to stream through the pipes all the pipes do have the same level, consequently they play the same tone.

Ca. 10 min. Watch the video also on Youtube or Vimeo.

Just the pulse is controlled externally. But the individual activity relies on the local interaction between the neighbouring pipes, which are connected by cables to exchange their states. Similar to a "wave" in a football stadium a relatively simple neighbour rule drives the pipe's activity deciding to light up and to play a tone. The activity trend is expressed in a special way: The water column rises or falls depending how active a pipe was during the last steps. This changes the pitch of the played tone, but also its timbre.

Aura calculata was realized in Winter 2016 in collaboration with the organ buildersJäger & Brommer from Waldkirch in occasion of the exhibition XX oder der Mummelsee in der Pfanne at the Städtische Galerie Offenburg.

sine tone environment

Aura calculata is a permanent sound installation for the lobby of the Lehmann-Zentrum of TU Dresden designed by Tim Otto Roth in 2015. The smallest discrete unite of this environment are the 39 "sound pixels": These electronically autonomous loudspeaker sculptures made of translucent acrylic glass exchange their status locally with their neighbour pixels by cables.

The speakers at the leftmost and rightmost position are connected behing the wall with a long cable, so the sound pixels are arranged in a cyclic order. The line of loudspeakers represents an elementary calculation process. The illumination of a sound pixel or playing a sound is based on the principle of a simple addition, similar to a human wave in a stadium. The activity of each sound pixel is a reaction to the activity of its immediate neighbours. Four different neighbourhood rules can be selected for the pulsing control sending an accelerating or decelerating meter. Given a chosen rule, exactly one neighbour being active means that the sum of all active neighbours equals one. Thus, the sound pixel plays a sound and lights up on its own in the next step. A sound pixel that has predominantly been active or off during the recent steps changes its colour and slightly its pitch upwards or downwards according to a metric scale. A continuously changing self-organizing sound tapestry is woven in the absence of a central directing instance. The sine tones recompose locally to different sounds of an organ like timbre.
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Aura calculata is powered by Bull GmbH.


Aura calculata is a musical adaptation of so called cellular automata. This self-organization principle is a kind of simple network revealing a complex behaviour caused by simple local interactions in the absence of a central directing instance. These neighbour rules function similar to a human wave in a stadium, where the actors stand up in case one of their neighbours stood up in the previous step.

This simple form of communication in a local field of neighbours, Tim Otto Roth is exploring in close collaboration with Prof. Andreas Deutsch at TU Dresden, inspired Tim Otto Roth to formulate the "Pixelsex" principle: Understanding sex as a kind of local communication and interaction the artist examines how in a field of discrete units (Pixels) complex process can be modeled just with simple local rules. This model is established in the science for quite some time. At the end of 1940s the mathematician John von Neumann and the physician Stanislav Ulam developed the first concepts. The idea inspired also Konrad Zuse – the inventor of the first functioning computer – to think about physics taking place in a "calculating space".

If you change the "wave" rule (left) simply, telling a soundpixel to be active if eigther the left or the right neighbour is active you get a pattern (right).

Tim Otto Roth animates such a "calculating space" by a special analysis to reveal its dynamics by the medium of sound. Depending on the number of sound pixels a rule set is defined how to react on the local activity. The 39 loudspeaker sculptures in Dresden interact according to simple addition rules. Given a chosen rule, exactly one neighbour being active means that the sum of all active neighbours equals one. Thus, the sound pixel plays a sound and lights up on its own in the next step. Via the control unit the visitor can switch between four different addition rules. The organ sculpture uses a different rule set as with the reduced number of just 18 organ pipes additive rules don't show a dynamic behaviour anymore.
The director of the Center for Art & Media (ZKM) in Karlsruhe, Prof. Peter Weibel emphasized in a public conversation with the artist, that the spatial arrangement of the pipes and the network model are characteristic for a music of the 21st century.

Related projects:

music & science

Both versions of aura calculata do have in common, that in the beginning the sound pixels play the same tone. The individual pitches change over time due to the Pixelsex principle. At the speaker version all the active sound pixels play a tone at the standard pitch A4 at 440 Hz and light up green. Step by step the pitches drift up and down, weaving a sound carpet of beats changing its character by the listener's position. The colour spectrum of the light is connected to the played pitch: Tending to higher tones the soundpixel changes its colour towards blue. If the tones are getting deeper the colour of the loudspeaker changes to yellow and red. If a sound pixel reaches a pitch threshold the whole system is reset.

At the water organ the water level and consequently the starting frequency of all pipes is defined by time interval opening the inflow valves, so the water levels of the pipes can balance with the central reservoir column. During operation water flows in and out due to sound pixels local activity. Changing the water level not only changes the pitch of the sound, but also its timbre. By that way sounds recompose in space creating beats and weaving an oscillating sound carpet – the organ's expansion as an instrument by a microtonal dimension.
Voicing the pipes for aura calculata the organ builders Jäger & Brommer made a remarkable discovery. It is commons sense that an organ pipe has a single optimal sound (with a clear fundamental tone) due to the pipe scaling (mensur). But the surprise of the organ builders the pipes for ‚aura' could be voiced in that way, that depending on the water level they can play two optimal sounds.

Aura calculata opens the system of the Western tone scale by changing pitches not logarithmically, but metrically varying the wavelength of the generated sine tones in millimeter steps. Consequently the audible differences become smaller playing deep tones, but they are significant at higher pitches. The pitch differences of the water pipes depend on the opening times of the inflow and outflow valves, but also the changing pressure of the water column in the individual pipe and the water reservoir.


Aura calculata is a modular system of autonomous sound producing electronic boards, the so called sound pixels [SP]. These circular white electronics especially designed for aura calculata can be connected to a simple network: Via a cable interface they can exchange their state with a maximum number of four SP . They can express two states: When active a SP lights up and plays a tone, else light and sound are switched of. For the loudspeakers the sine tone is generated by an integrated function generator. For the organ a valve is controlled opening and closing the air supply in an individual air channel.
The control unit only communicates important general parameters, as the neighbour rule, and sends an analogue clock pulse. When a SP receives the clock pulse it analyzes the states of its neighbours and calculates its own next state according to the current rule. The neighbours result from the direct cabling. Typically a SP is connected with two neighbours resulting in a ring like network.
The trend of a SP's activity can be expressed in various ways: changing the pitch of the sine tone, the water level or the colour of the led. For the sine tone version the artist designed little loudspeaker sculptures made of translucent acrylic glas functioning as luminant bodies. The organ sculpture is made of transparent acrylic glas and metal elements creating a minimalist functional structure making the whole air and water supply system transparent. The organ pipes arranged as a circle around the reservoir tube in the center are fixed to a truss made of acrylic tubes and metal clamps. The pipes were constructed and tuned by the organ builders Jäger and Brommer from Waldkirch. The complete organ was built by Tim Otto Roth and his team in his studio in the Black Forest.

Special thanks to:

Elektronics: Ingenieurbüro Dipl.-Ing. (FH) Gary Grutzek, Köln
Assistence loudspeaker contstruction: Wonbaek Shin
Montage Dresden: Dipl.-Ing. Michael Reyl, Köln
Architects Dresden: Code Unique
Project monitoring Dresden: Prof. Dr. Andreas Deutsch, Daniel Hackenberg, Dietmar Augustin

Pipe builders: Jäger & Brommer, Waldkirch
Metal works: Schlosserei Franz Birk, Oppenau
Lasescuttings acrylic glas: Uwe Schüler & Jördis Drawe,Kulturgüterschuppen Dusslingen
Processing acryl glas for the organ: Andreas Langenfeld; Benjamin Größle
Assistence organ construction: Andreas Langenfeld; Elisabeth Nägele; Johanna & Willi Seidler; Silke Hodapp

project management: Miriam Seidler


Scientist have worked for quite some time with various self-organization principles to find models for instance for the growth pattern of the small mussel Conus pennaceus, for jams as an expression of traffic flow or the growth of tumor cells. Tim Otto Roth's examinations on the so called cellular automata in the context of his artistic oeuvre are quite revealing, as he discovered a new local dynamics. As each soundpixel analyses its activity during the last steps the resulting temporal attractors draw a different picture of the dynamics in comparison to established classifications of cellular automata.
For the exhibition XX oder der Mummelsee in der Pfanne  Tim Otto Roth has published a special poster edition as a kind of visual illustration of the dynamic activity of the organ installation. This offset edition on bookprint paper limited to 200 posters functions as kind of score for aura calculata, as the pitch dynamics of all the 18 soundpixels can be followed as oscillating curves over 4000 steps. r.


7 March – 14 June 2020 ### Logische Phantasien, solo show featuring the water organ at Kunsthalle Jesuitenkirche, Aschaffenburg, D

13 March – 30 April 2019 ### das erste mal zum zweiten mal. 20 Jahre, presentation of the 23 channel speaker version of aura calculata in the context of a group show at Marburger Kunstverein, Marburg, D

8 May 2017 ### aura calculata, is one of the nominated works for the STARTS - Grand prize of the European Commission honoring Innovation in Technology, Industry and Society stimulated by the Arts

February 2016 ### Premiere: In occasion of Tim Otto Roth's exhibition XX oder Mummelsee in der Pfanne at the Städtische Galerie Offenburg aura calculata is realized for the first time as water organ:

deutsch To turn on English captions please click the CC button in the player's bottom toolbar. Ca. 10 min. You can watch the video also on Youtube.
More about the museum exhibit running from 19 February - 29 May 2016 in Offenburg:

media response

11 November 2017, Mathematical Socialism: Tim Otto Roth Lights Up Hanoi, feature and interview by Robert Barry, The Quietus

September 2017, Aura calculata, challenging the tonal scale, review by Paul Prudence, NEURAL #57

October 2015 Aura Calculata – die Klang- und Lichtkunst von Tim Otto Roth siedeln an der Schnittstelle von Kunst und Wissenschaft, by Helga de la Motte-Haber, Neue Zeitschrift für Musik 05/2015, pp. 34-37

June 2015 Aura calculata - am 20. Mai wurde im Foyer des Lehmann-Zentrums die permanente Klanginstallation von Tim Otto Roth eingeweiht, Dresdner Universitätsjournal 10/2015

For further reviews on the organ installaction and press pictures please consult the press page of the Offenburg exhibition.