Hierarchical System Design in Live Audio-Visual Improvisation

This article explores the usage of a hierarchical system to interact with audio-visual systems via digital mapping interfaced through a gaming controller.  It will investigate a system developed called HLSC (Hierarchical Lindenmayer inspired Structure of Control) featured in the Audio Visual Ensemble 2014 project as part of the Digital Media Studio Project course at The University of Edinburgh.  It will not investigate hardware controllers, but will acknowledge the unique capabilities when pairing gaming devices with real-time, audio-visual systems.  The device used for the Audio Visual Ensemble project is a PS3, Dualshock controller.  The methodology of controller assisted performance used by the HLSC infrastructure can be applied to any comparable hardware controller.

A note on gaming devices

            Most modern gaming devices are designed for spontaneous, multi-dimensional interactions in a virtual gaming world.  For this reason, they are naturally inclined towards controlling similarly complicated interactions in the audio-visual realm. Todd Winkler (2001) writes about computer controllers:

“Thought should be given to the kinds of physical gestures used to send data to the computer, and how specific movements can best serve a composition….Playing new sounds with old instruments only makes sense if the old technique is valid for the composition” (p.37)

With the computer’s ability to create sound without a physical medium, controller decisions can and should be tailored to specific performance situations.  There are documented ways of using gaming controllers within the maxMSP programming environment (Jensenius 2007, p.106).  However, most of these utilize simple and linear systems for users with a “plug-and-play” mentality.  While simple for immediate use as a real-time performance tools, these systems have limitations when used to control multiple systems in creative and improvisatory ways. Jensenius elaborates:

“A common solution to master such a complex system, i.e. consisting of many different and connected parts, is to create presets that define a set of parameters that work well together. These presets may then be used for further exploration of the sound synthesis model. However, the result is often that many people only use the presets, and never actually control the sound model more than changing from one preset to another. This again makes for a static and point-based type of control” (p. 101).

This type of static control which relies heavily on presets was not conducive to the interactive aesthetic of the Audio Visual Ensemble 2014.  I developed the HLSC system to separate myself from the computer screen, control complex systems, and facilitate gesture driven interaction with ensemble members.

Inspiration for model

Originally inspired by structures produced by Lindenmayer systems, these tree-like hierarchies are a good way to visualize how this control system works.

Courtesy of Wikipedia: http://en.wikipedia.org/wiki/L-system

Starting from level N=0, we see from this diagram that at each level contains more and more elements.  Although originally designed to model organic growth,  I imagined these levels as a parent-child system of control.  For example, the A and B in level n=1 control the elements in level n=2 which in turn control the elements in level n=3, etc.

To apply this structure to a system of control, the ability to go from level to level was paramount.  By moving through levels, macro and micro controls can be accessed by the same device.  Further, the self-similar nature of the Lindenmayer structure allows different levels to have familiar shapes of control.  For the application of this structure to the PS3 controller, I utilized button combinations and bumpers to access and gate data flow.

Controller application

Please refer to this diagram from the official PS3 website for exact controller surfaces referenced in this section.

PS3_ControllerOn this hardware controller, one stream of the HLSC system taken to its end could can be represented as such:

DMSP_Micro

Please click to expand

Only one element of each level is expanded in this diagram, but each element of the same level could be expanded in an identical way.  A more conceptual representation of this could structure is as follows:

Please click to expand

Please click to expand

This representation shows a multi-level, hierarchical structure similar to the Lindenmayer system seen earlier.  To move between levels and gate information for specific settings, a combination of home and bumper is used at the Top-Level, bumpers to gate information at the Lock-Level, and either alt or start at the Surface-Level to access alternative, lower level parameters.

For pictures of the patch and more details about its use in performance, please refer to my Submission2 blog post.  To download the interfaced used to connect and package data from my PS3 Dualshock controller, download the patches from this link:

www.dropbox.com/s/vwqj59aahujeccm/ControlSys.zip

Complexity and creativity

By using HLSC, levels of one-to-one and one-to-many interactions can be accomplished without physically touching a computer.  With the aesthetic goal of live interactivity for my performance with the Audio Visual Ensemble 2014, I needed to interact with multi-dimensional parameters of two visual systems, two musical systems, and combinations of these systems in real-time.

Despite working with so many systems and controls simultaneously, less than 10% of the possible controls in the HLSC system were used (only two of the “Top-Level” branches are partially utilized).  However, the vastness of this system allowed me to make mapping decisions based on artistic decisions instead of system limitations.  For example, mapping orientation data to be controlled by gestures during more intimate sections where dialogue is especially important.

Although parameters were mapped scrupulously to be logically arranged, at times I found myself forgetting what exact surfaces of my controller accessed what.  However, these unpredictable results were often aesthetically rewarding.  Electronic composer Brian Eno dreams of getting lost in a complex, self-generating system similar to HLSC:

“But what if the synthesizer just ‘grew’ programs? If you pressed a ‘randomize’ button which then set any of the thousand ‘black-box’ parameters to various values and gave you sixteen variations. You listen to each of those and then press on one or two of them—your favourite choices. Immediately, the machine generates 16 more variations based on the ‘parents’ you’ve selected. You choose again. And so on. The attraction of this idea is that one could navigate through very large design spaces without necessarily having any idea at all of how any of these things were being made” (Dahlstedt, 2007)

This passage demonstrates the creative potential of a complex system even when a performer is lost.  With simpler one-to-one mapping, all combinations of interaction can be quickly exhausted, but with a complex system like HLSC, the possibility for unexpected interactions is much greater and therefore can foster creative results.

 Conclusion

The HLSC system is one that I will be utilizing and further developing in the future. Its multifunctional, high-level control allows for more meaningful, audio-visual interactions than static presets.  The ability to negotiate and improvise with many nested levels of control in real-time makes it a valuable performance tool.  Future application to the API of DAWs such as Abelton Live 9 or Bitwig could allow an average game controller to be used as a powerful production tool.

An interesting study for the future would be to develop rules for Lindenmayer systems of control based on a particular controller specifications.  By formulating and testing equations based on the number of surfaces and the dimensions in which those surfaces function, perhaps a HLSC-like system could be autonomously generated without having any experience with a specific controller.

 

References

Dahlstedt, Palle. 2007. Evolution in Creative Sound Design. In Evolutionary Computer Music. Eduardo Reck Miranda MSc and John Al Biles BA MS, eds. Pp. 79–99. Springer London. link.springer.com/chapter/10.1007/978-1-84628-600-1_4, accessed April 24, 2014.

Jensenius, Alexander Refsum. 2007. Action-Sound : Developing Methods and Tools to Study Music-Related Body Movement. www.duo.uio.no//handle/10852/27149, accessed April 24, 2014.

L-System. 2014. Wikipedia, the Free Encyclopedia. en.wikipedia.org/w/index.php?title=L-system&oldid=605470900, accessed April 25, 2014.

Sony. n.d. [Diagram of PS3 controll]. Retrieved from support.us.playstation.com/app/answers/detail/a_id/960/related/1/session/L2F2LzEvdGltZS8xMzk4MzgzOTUwL3NpZC9XUUNrQ0RTbA%3D%3D

Winkler, Todd. 2001. Composing Interactive Music: Techniques and Ideas Using Max. New Ed edition. Cambridge, Mass.: MIT Press.

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