downloaded from Tim Perkis' www page may 15 1995 776w


AN EXPERIMENTAL SHARED ACOUSTIC ENVIRONMENT BY TIM PERKIS * What is OpenField * How to use OpenField * How OpenField Works

About OpenField

OpenField is an experiment in setting up an "acoustic ecology", in which agents defined by web clients take life and interact freely in a shared acoustic environment which is multicast on the internet. Users contact a WWW server to receive a form with which they set various parameters to design a musical agent. When the form is submitted, their agent is started up, creating a voice which goes into the mix. The entire mix is continuously multicast on the internet and can be monitored with VAT (the video & audio teleconferencing tool) at any site having an MBONE connection.

Consider the analogy of a natural environment: it's amazing to me how the various birds and insects "multiplex" the channel of the outdoor acoustic space, each species differentiating its signal from the others in the space. I'm interested in seeing what kind of ecology may emerge as multiple simultaneous users try to create agents which can be heard. The motivation to hear yourself, or the result of your own actions, is, I hope, enough to drive people to try to create agents with recognizable signatures. Without the option of playing loudly, or continuously, in order to be heard, each user must come up with a sound which is at once distinct from the other voices sounding, and in harmony with them in the sense of basing its nature on the acoustic world the other voices define.

Another analogy to explain the focus of OpenField would be the set of sounds used by a language, or the set of graphic marks used by an alphabet: they develop a harmony by all evolving towards maximizing their mutual distinctiveness.

Using OpenField

To play OpenField, users must have Mosaic 2.x or greater for the web client and in order to listen to the audio of OpenField, you must have the VAT multicast audio software and your site must be configured to accept IP multicast.

If you are not receiving the audio, PLEASE do not submit an agent control form! I'd rather have the environment determined by people who are listening! There's no "payoff" for you in submitting a form: only the audio changes when a form is submitted.

(At PARC, first "enable mcast" and "enable www" if necessary.) 1. Open a multicast session directory tool by typing "sd&". 2. Select the "OpenField Sound Environment" session and press "Open" in the sd window. (You may need to wait a couple of minutes for OpenField to appear in the menu.) 3. Click Here to go to the OpenField control form.

How it works.

I'm using a MIDI synthesizer and sampler, limiting my sound palette to short noise and tone bursts, (chirps, creaks, clicks, etc.) and short vocal sounds, all of which are modulated in pitch and amplitude in continuous variation by the defined agent. An agent consists of a semi-randomly assembled piece of code which has rudimentary hearing (it knows only how many other voices are sounding at the current instant), and which plays short sequences consisting of some subset of the set of basis sounds. Users define aspects of their agent's behavior, by selecting the basis sounds for the agent's voice, and some general behavioral parameters about its timing.

In much of my recent musical composition work I've been working with genetic programming, in which populations of tiny computer programs in a special language are randomly mutated and bred under constraints which lead to evolution toward a goal. This work follows from that, in that the agents' control programs are created by a process of constrained randomness, generated at random with statistical properties (the distribution of different op codes ) set by the user controls.

TIM PERKIS has been working in the medium of live electronic and computer music for many years, performing and recording extensively in North America and Europe. His work has largely been concerned with using computer media to explore the emergence of life-like qualities in complex systems of interaction. He is the cofounder of The Hub, a computer network band. He has performed at such venues as the San Francisco Museum of Modern Art, Apollohouse and The Royal Conservatory in the Netherlands, Fylkingen in Stockholm and the Academie der Knste in Berlin. His occasional critical writings have been published in The Computer Music Journal and Leonardo.. In 1993 he was composer-in-residence at Mills College in Oakland California, and in 1994 received a residency from Xerox PARC. Recordings of his music are available from Artifact Recordings.