Artemis MoroniIA/CTI

Jônatas ManzolliNICS/UNICAMP

Fernando Von ZubenFEEC/UNICAMPRicardo GudwinFEEC/UNICAMP

An Evolutionary Approach

Applied to Algorithmic Composition

http:/ /www.ia.cti.br/~artemis/voxpopuli

BRAZIL

VOX POPULI is WINNER of

The International Competition Dream Centenary Computer Graphics

in Aizu, Japan

http://www.ia.cti.br/~artemis/voxpopuli

VOX POPULI, what is it ?

Ø an end-user interface that allows real time parametric control of sound events;

Ø an interactive environment in which Evolutionary Computation is applied to AlgorithmicComposition;

Ø uses genetic algorithms to generate and evolve a sequence of chords played as MIDIdata.

In VOX POPULI…

Individuals of the population are defined as groups of four voices.

These voices are randomly generated on the interval [0…127], which corresponds to MIDI events:

pitch is represented by the MIDI note table;

duration depends on the rhythmic genetic cycle;

loudness is related to MIDI velocity table;

timbre is given by the General MIDI instrument definition.

Ø In each generation, 30 chords are produced and evaluated;

Ø They are internally represented as a chromosome with 28bits, composed of 4 words with 7 bits:

1010111 1100110 1100111 1110001

http://www.ia.cti.br/~artemis/voxpopuli

Rhythmic Genetic Cycle

REPRODUCTION

CROSSOVER

MUTATION

FITNESS1010101 1011101 0000101 11101011011111 0001101 1101101 00001011010001 0111101 1100111 0101101

1011111 0001101 1101101 0000101Current best chord

interface

Voices Range Criterion

Consonance Criterion

Co(N1, N2) = Intersection(N1, N2)

Musical Fitness

•Octave FitnessO = Max(Oc(xi ))/4, i = 1, 4;

•Melodic FitnessM(N1, N2, N3, N4) = Max[CId(Nj)],j = 1, 4;

whereCId(Nj) = Co(Nj, Id).

•Harmonic FitnessMax(Co(N1, N2), Co(N2, N3,), Co(N3, N4), Co(N4,

N1)

Musical Fitness

F(O, M, H) = Octave Fitness +

Melodic Fitness + Harmonic Fitness

Interface and Parameter Control

Melodic ControlOctave Control

Biological ControlRhythmic ControlOrchestra Control

Interactive Pad Control Red Curve

Melodic ControlOctave Control

Blue CurveBiological ControlRhythmic Control

Fitness Displays

• Notes fitness, on the top;• In the middle, a bar graph shows the four voices

(bass, tenor, contralto, soprano) and their value• The last shows the melodic, harmonic and octave

fitness plot.

Sound Examples

We would like to thank our fellow student Leonardo

N. S. Pereira for developing the

routines to evaluate the consonance criterion. This

work was supported by FAPESP (São Paulo State

Research Foundation, process no. 95/08479-3),

CTI (Technological Center for Informatics), and CNPq (process no. 300910/96-7).