ICAD-2002 Liquiprism

International Conference on Auditory Display, Kyoto, July 2002

Liquiprism - Generating Polyrhythms
with Cellular Automata

Alan Dorin

http://www.csse.monash.edu.au/~aland

Centre for Electronic Media Art
School of Computer Science & Software Engineering
Monash University, Melbourne, Australia

Outline

Motivation
Previous methods & music
Cellular Automata

Liquiprism as it is
Liquiprism as it is becoming
Conclusions

Motivation (personal)

I have only two hands, two feet and limited co-ordination...

...I love complex rhythms that I can't possibly play!
Complex behaviour from simple rules ...life...

"Sometimes everything just comes together and suddenly you've created this wonderful organism" [Reich]

"And as the music grows in depth and complexity of texture, so the time taken for the sound organism to make itself felt is extended" [Nyman of Glass' music]

I wanted an interactive and semi-autonomous alternative to MIDI drum editors and step sequencers

Previous music

Xenakis: Pleiades
Reich: Drumming, Music for 18 Musicians, Sextet...
Autechre: ep7
Plastikman: Artifakts
Jazz & Cuban, African, Chinese or Hindu percussion music

...exploit polyrhythmic structures for their 'spark'

Previous / related methods

Play it
(multiple players, hands, mallets or fingers)
Mechanize it
(tape recorders, metronomes, clocks, revolving arms, suspended microphones)
Compute it (electronic sequencers, "ordinary" cellular automata, complex systems)

Two one dimensional CA's, Wolfram '84

Boolean Sequencer, Dorin '99

Turbulence (detail), McCormack '94*

Cellular Automata

Connected set of finite state-machines (usually arranged in a square grid).
Synchronous update.

A node's future state depends on the states of nodes in the network designated as its neighbours and its transition rule/table.

	-
-	-	-
	-

-	-	-
-	-	-
-	-	-

4 - neighbourhood region

8 - neighbourhood region

A node may read/feedback its own state as a self-input.

Sample Cellular Automata: The Game of Life

8 neighbours for each cell
2 states per cell (ON/OFF)

Transition rules

if (current-state ON)

if (exactly 2 or 3 neighbours ON)
{ next-state ON }

else
{ next-state OFF }

else // current-state OFF

if (exactly 3 neighbours ON)
{ next-state ON }

else
{ next-state OFF }

Screenshot from Easy Life v2.0 by Reggie McLeod

Sample cyclic patterns


Spinner (animated)	1	2	1

Glider (animated)	1	2	3	4	1

Liquiprism

Set of 6 cellular automata grids arranged in a cube
Neighbours to a cell may cross cube edges
Cube faces may operate under different transition rule sets
Active nodes trigger MIDI events (2 are selected from a larger number)
Cube faces are assigned different MIDI channels
Pitches rise a semi-tone for one grid space across a face, and a fifth for one step up a face

Transition rules (set #1)

if (current-state ON)

if (exactly 2 or 3 neighbours ON)
{ next-state ON }

else
{ next-state OFF }

else // current-state OFF

if (>= 4 neighbours ON)
{ next-state ON }

else
{ next-state OFF }

Transition rules (set #2)

if (current-state ON)

as above

else // current-state OFF

if (neighbour-below ON) AND (1in3 chance)
{ next-state ON }

else
{ next-state OFF }

User Interface - Current

Simple mouse-based rotation of the cube
Random activation of the cells on the front face triggered by mouse clicks


Current interface
web-movie (4Mb)	large-movie (46Mb)

User Interface - Under development

Sculptural prism of light
Activation of the cells on the faces according to position and movement of visitors to the installation

Interface under development	web-movie (5.5Mb)

Conclusions

As a music or polyrhythm generator this is 'OK' but not great
As a screen-based interactive it is of limited interest as it does not seem to have a strong 'presence'...
Perhaps it:
- Requires a more interactive approach to response and control
- Requires a physical form which can be experienced without the (apparent) barrier of the screen