GEOGRAPHY: A TWO-COMPONENT SYSTEM FOR SOUND ORGANISATION

Fondazione ISI

Torino, Italy, 01/12/2004

Andrea Valle [email protected]

GEOGRAPHY: A TWO-COMPONENT SYSTEM FOR SOUNDORGANISATION

Andrea Valle ([email protected])

CIRMA-Università di Torino

Fondazione ISI

GEOGRAPHY: A TWO-COMPONENT SYSTEM FOR SOUNDORGANISATION

ACT - Art Complexity and Technology

Torino, Fondazione ISI May 5-6 2005

GeoGraphy

What is GeoGraphy?

-a formal system

-for the algorithmic control of sound organisation

-based on sound objects

A. Valle, V. Lombardo, “A two-level method to control granular synthesis”,Proceedings of XIV CIM, Firenze, Centro Tempo Reale, 2003

GeoGraphy

What is GeoGraphy?

The system features two components:

1. Component I: organizes sound objects into a graph structure

2. Component II: places the graph in specific locations of a space.

A sound organisation (i.e. composition, “soundscape”) is atrajectory in the space

appropriately interpreted to control a number of parameters of physicaland musical relevance.

GeoGraphy

What is GeoGraphy?

1. Each graph structure represents a set of relations between vertices,which can be thought as objets sonores.

2. Sound objects as defined by Schaeffer are symbolic objects encodingsonic properties apt to be used in compositional practice.

They are considered meaningful-to-the-ear objects, while physicaldimensions need a continuous monitoring to be musically relevant.

3. Consequently, the system can be expanded from granular synthesis (i.emicro-time scale) to instrumental composition (i.e. macro-time scale)

GeoGraphy

The system

Terminology

- A composition is a set of sequences

- Each sequence is a sequence of sound objects

GeoGraphy

The system

Composition as a set of sequences (s.o. sequences)

(In a musical way:

a “polyphony” made up of many “voices”.

Figure = score)

s.o. 1.1

s.o. 2.2

s.o. 3.2 s.o. 3.3

s.o. 1.2

s.o. 3.1

s.o. 2.3

s.o. 1.3

s.o. 2.1 s.o. 2.4

Seq. 1

Seq. 2

Seq. 3

GeoGraphy

The system

Components of the system

Component I: a graph-based generator of s.o. sequences (i.e.sequences)

Component II: a map-based controller of s.o. parameters.

GeoGraphy

Graphs

Component I: The sound object generator

The sound object generator is based on directed graphs

multigraph: it is possible to have more than one edge between twovertices.

Each graph is a set of vertices and edges

Vertices: sound objects

Edges: the sequencing relation between two sound objects.

GeoGraphy

Graphs

Edge label: temporal distancebetween the onset times of thetwo s.o. connected by the edgeitself

Vertex label: s.o. duration

loop

Multiple edgesbetween vertices

Graph 1: the general case

multigraph with several connections (almost completelyconnected) and loops

GeoGraphy

Graphs

- A sequence (s.o. sequence) is a path on the graph

- In case a graph contains loops, sequences can also be infinite

- Sound object duration and delay of attack time are independent

it is possible to superpose s.o.

(vertex label > edge label).

GeoGraphy

Graphs

A Stravinskjian example:

Graph modelization of a fragmentof the Sacre du Printemps,Danse sacrale, 142-147.

Red letters: 4 sound object

Black letters: regions ofSchaeffer’s typological space)

Numbers: durations o edges insemiquaver

GeoGraphy

Graphs

How to create a sequence?

sequence generation requires the insertion of graph actants

Graph actant: dynamic element which generates the s.o. sequence

- initially associated with a vertex (that becomes the origin of a path)

- the actant navigates the graph by following the directed edgesaccording to some probability distribution.

- The graph actant’s path on the graph generates the sequence

GeoGraphy

Graphs

Multiple independent graph actants can navigate a graph structure at thesame time

it is possible to generate more than one sequence (s.o. sequence).

In a composition there are as many sequences as graph actants

GeoGraphy

Graphs

“The Percussion Room Frame” - Part I

- A large room is filled with a set of percussions

- One or more percussionists are playing on them in the same time

- In order to play, all the players have to follow certain rules defining foreach percussion:

1) how much time to hold the note (playing in tremolo…)

2) how much time to wait before hitting the next percussion

3) which percussion would be the next one to be played

GeoGraphy

Graphs

“The Percussion Room Frame” - Part I

Percussions --> Vertices

Graph actants --> Players

Rules --> vertex labels (time to hold)

--> edge labels (time to wait)

--> probability distribution determining which edge to bechosen

GeoGraphy

Graphs

The Graph 1 and a short sequence

Start: 4

Path: 4-1-1-1-2-2-2-3-1-3

Graph 1

GeoGraphy

Graphs

Graph 2: the simplest graph

a graph with one vertex and one edge that loops on the unique vertex.

Resultant grain sequence:

exact repetition of the grain associated with the vertex; each repetitionstarts after 63 milliseconds with respect to the beginning of theprevious repetition.

Graph 2

GeoGraphy

Graphs

Graph 3: Subgraphs

Graph 3 consists of three disconnected subgraphs, each with one vertexand three edges that loop on the vertex itself.

Graph 3

GeoGraphy

Graphs

Assuming a single actant on each subgraphs, the Graph 3 generates threesimultaneous streams of sound objects (here grains of sinusoids).

GeoGraphy

GraphMap as a Control Space

Component II: The s.o. controller

- The graph is positioned in a space (hence GeoGraphy)- Parameter values are controlled by navigating the space

(Component I: single sound streams -sequences- have been definedthrough the generation of the graph)

Component II:

1. Graph is distributed onto a map.

2. The composer designs a trajectory that allows to decide how theseveral sequences contribute to the piece.

GeoGraphy


1a. Space

- Theoretically, the space can have any number of dimensions

- Typical applications are limited to the Euclidean space (examplesfeature only two dimensions).

1b. Graph Positioning

- each vertex is associated with coordinates in the space.

GeoGraphy


2a. Trajectory: a second actant (the Control actant) navigates atconstant rate in the space following a trajectory.

2b. The Control actant is given a certain threshold determining the radiusof a circle surrounding him (audibility radius). What is out of thecircle is filtered away.

2c. Distance is the general controller:

The nearer is a trajectory to some vertex, the higher is the value of someparameter for the sound object represented by that vertex

GeoGraphy

A random graph of 100vertices and 80 edgesexplored by a trajectory(orange line): arrowheads indicate direction ofthe Control actant, thelight violet regionrepresents the audibilityradius

(made with Graphista!)

GeoGraphy


2.d Another parameter is calculated

Considering the space actant as a directed human head:

- the displacement of the vertex from the frontal and the lateral axes(pan)

GeoGraphy


summarizing

Generation process:

1. Each vertex emits a s.o. (determined by the passage of the graphactant).

2. When a s.o. is generated, the device calculates the distance betweenthe space actant and the vertex.

3a. If the distance > audibility radius (threshold value) , the event isfiltered off

3b. Else: distance is used as a general control parameter.

GeoGraphy


“The Percussion Room Frame” - Part II

- A Listener enters the Percussion Room and explores it

- In each position, the Listener can hear some percussions, other aretoo far

- The way the percussions sound depends on the relation between thepercussions and the Listener (i.e. the farther the weaker)

GeoGraphy


“The Percussion Room Frame” - Part II

Listener --> Control actant

Threshold --> resolution of an audibility radius

Transformations --> as a function of distance

GeoGraphy

Composing with GeoGraphy

1. Compositional work results form the interaction of thetwo components.

A two-step process:

1a. Definition of the graph structure

(1b. Definition of the graph acoulogical properties)

2a. Definition of exploration strategies

(2b. Definition of space’s acoulogical properties)

(GeoGraphy is abstract from b.)

GeoGraphy


1. Definition of the graph structure

Each space has its unique morphology resulting form bothtopological, metrical and acoulogical information (Schaeffer)

The morphology characterizes unambiguously a space,determining its identity

GeoGraphy


2. Definition of exploration strategies

But this morphological identity can be accessed exclusivelythrough the exploration made by the the Control actant

Control actant:

- Eliminates some events (see audibility radius)

- Transforms all the sound material as a function of thedistance and pan parameters.

GeoGraphy


Morphological information (topological, metrical and acoulogical)must be reconstructed from the surface level, resulting formthe interaction of the two components.

GeoGraphy models a 2nd order cybernetics system in which theobserver is included in the system itself. Observablebehaviour depends on their interaction.

Meaningful properties do not depend on the “complexity” of eachlevel but emerges from their interactions.

Complexity is a relational property

GeoGraphy


The reconstructed graph (on a space 100x100)

Hypothesis

a) 1 monodirectional circuit (each vertex is connected with oneother, without repetitions of linked vertices)

b) 1 Graph actant

c) Trajectory SE-NW

d) Audibility radius

What are the consequences of exploration?

GeoGraphy


The reconstructed graph (on a space 100x100)

AR = unrelevant AR = 20 AR = 10

GeoGraphy

Non-determinism

1. Map space is filled not with actual events but only with potentialevents (vertices)

- it is possible that a sound object is emitted at the very moment inwhich the space actant scanning the timeline trajectory is passing

- it is not necessary, as it depends on the grain generator

(it is like scanning a sky filled with pulsating stars).

GeoGraphy


Different trajectories reveal different aspects of the space

Typically:

A composition is a set of pieces, each one dedicated to a differentsexploration of the same space.

Composing is like shooting with a camera

“Moving around a sound object (like a sculpture)”

(see Satie: Gymnopedie I-III, Sciarrino: passim)

GeoGraphy


2. Composition is sound organisation

Relevant level: organisation of sound objects

(Varèse: music as “organised sound”)

The relevant information concerns sound quality (i.e acoulogicalinformation)

GeoGraphy


3. Composition is time organisation

More radically:

Sound objects --> sequences of events

GeoGraphy --> A device for temporal punctuation: a “chrononomictool” (Stravinskij: music as “chrononomie”)

GeoGraphy acts as a general sequencing environment. It does notassume to work at a particular time scale, simply to work “intime” (en temps)

GeoGraphy



GeoGraphy can be used for instrumental composition as forgranular synthesis (microtime-scale)

GeoGraphy



Instrumental composition

Example

Vertices: notes or short modal phrases

Distance can control timbral parameters (“energy”):

- the continuum tasto-ponticello (for strings)

- tuning micro-alteration

- dynamics etc.,

GeoGraphy Instrumental composition

Escatologie portatili for string quartet and flute-IIIa-c, Tre studi sullo spazio figurativo

GeoGraphy Instrumental composition

Studi per Anni Albers, IV

for 15 strings

A space filled withdisconnected,looping vertex(trichords).

Noise pattern (nails onwood) asbackground

GeoGraphy

Granular synthesis

A definition

-various kinds of synthesis techniques

-based on a grain representation of sound

-i.e. sonic events are built from elementary sonic elements of veryshort duration (5-150 msec)

Different organization techniques can lead to very different timbral andcompositional results

GeoGraphy

Granular synthesis

Time scale (Xenakis)

micro mini meso macro

(notes) (rhythm)

grains composition

?

GeoGraphy

Granular synthesis

The question: “how to move?”

from 1. single grain level (microstructure)

up to 4. compositional level (macrostructure),

possibly through:

2. note level (ministructure)

3. rhythm level (mesostructure)

Two main approaches to answer

1. Note approach

2. Stochastic approach

GeoGraphy

Granular synthesis

The Note Approach

microstructure is embedded in ministructure

• ministructure defines the sound objects

• granularity defines the timbre of each object

(Examples: drum roll, rolled phonemes, flutter-tongue)

Implemented in grain-based modules of DSP applications

GeoGraphy

Granular synthesis

The Note Approach

There is a logic gap between sound and structure

(as in traditional composition: an object has a granular nature, but thisfact has no consequences on composition, see fluttertongue ortremolo notation)

(up to 3 meso and 4 macro)1 grains 2 notes

GeoGraphy

Granular synthesis

The Stochastic Approach

granularity is a compositional feature

• Pulviscolar matter

• Requires textural shaping

“unite sound and structure” (Truax)

(avoiding an “instrumental-music approach”)

1 grains 4 composition

GeoGraphy

Granular synthesis


Xenakis (Formalized Music):

Sound is thought as an evolving gas structure.

1. The audible field is modelled according to the Fletcher-Munsondiagram.

2. Each instant is described through the stochastic activation of certaincells in the diagram (a “screen”)

3. Each screen has a fixed temporal duration.

4. The sound/composition is an aggregatum of screens collected in a“book” in “lexicographic” order

GeoGraphy

Granular synthesis


Xenakis (Formalized Music):

GeoGraphy

Granular synthesis


Truax:

Massive sound texture

1. Juxtaposition of multiple grain streams (“voices”, like in polyphony)

2. The parameters of each grain stream are controlled through tendencymasks representing variations over time (i.e. timbre selection,frequency range, temporal density).

Quasi-Synchronous Granular Synthesis (QSGS)

GeoGraphy

Granular synthesis


Truax:

using tendency masks

Quasi-Synchronous

Granular Synthesis

(QSGS)

GeoGraphy

Granular synthesis


Roads:

Grains are scattered probabilistically over frequency/time plain regions(“clouds”).

1. Control of cloud global parameters (i.e. start time and duration of thecloud, grain duration, density of grains, etc.).

2. The compositional metaphor is painting (“pontillisme”), using differentbrushes with different (sound) colours.

Asynchronous Granular Synthesis (AGS)

GeoGraphy

Granular synthesis


Roads:

Painting a smooth

time canvas

Asynchronous

Granular

Synthesis

(AGS)

GeoGraphy

Expressivity issues: space

Typical granular synthesis techniques:

physical continuum time/frequency.

- scarce musical meaningfulness

- complexity in definining musical meaningful parameters

GeoGraphy

a general map space

- possibility of defining grouping strategies of vertices in the controlspace.

- possibility of embedding different topologies of musical featuresamong the ones proposed in literature.

(More later)

GeoGraphy

Expressivity issues: space

Granular synthesis with GeoGraphy.

(a typical case for complexity: the mass of grains has different propertiesfrom each grain)

Graph controls the generation of grain sequences (you do not want a finecontrol on it).

Some global properties depend on the morphological level and on thefiltering action of the Control actant

(More later)

GeoGraphy


4. “Algorithmic composition is an Art of Mapping”

Composing with GeoGraphy requires to specify the relationsbetween the features of the model and acoulogical properties(“Sonification”).

The set of GeoGraphy’s features must be mapped onto acoulogicalproperties in a consistent and “meaningful” way

GeoGraphy

Mapping:

(Going backwards)

I. Distance and pan

II. Space

II. Graph placement

IV. Graph structure and generation

GeoGraphy

GeoGraphy

Architecture of the System

GeoGraphy

DSP unitary module functionally split in two submodules

GeoGraphy

Processes audio not depending on distance(typically:generates sound object using vx mapping)

GeoGraphy

Processes all audio depending on distance(and on other parameters)

GeoGraphy

Distance: a simple figurative interpretation of the space

Psychoacoustics (distance, a complex topic: Blauert 1997: 116ff):

Monaural acoustic cues:

“

1. Spectrum conveys distance information as well, if the listener hasenough familiarity with the original sound […].

2. Intensity plays a major role, especially with familiar sounds in openspace […see Blauert 1996].

3. Direct-to-reverberant ratio affects the perception in closed spaces orreverberant outdoor environments

” (Fontana, Ottaviani e Rocchesso 2003: 207).

semiotic competence (“familiarity”) plays a major role

GeoGraphy

Distance: a simple figurative interpretation of the space:

Psychoacoustics (distance, a complex topic: Blauert 1997: 116ff):

“the first two cues model what happens outdoors in a large open field,where we sense the distance of a sound by its intensity and thefiltering effects of air absorption on high frequencies. Echo andreverberation cues model what happens in an enclosed space” (Roads1996: 463).

GeoGraphy


But: GeoGraphical space is not a physical one. It does not make sense toimplement a physical model (of what?)

Phenomenology

“the nearer, the ‘stronger’ and the brighter; the farther, the ‘weaker’ andthe duller”.

Figurative space: implementing semiotic categories

Cartoonification

Descriptive categories:

Jakobson, Fant&Halle 1952, Schaeffer 1966, Erickson 1975, Wessel1979, Risset&Wessel 1982, Cogan 1984, Slawson 1985

GeoGraphy


Spatial correlation of three categories for distance:

Distance: near <--> far

Dynamics: strong <--> weak (e.g. forte <--> piano)

Brightness: bright <--> dull (e.g. timbral spaces)

Reverberation: dry <--> wet (e.g. technology)

Three categories which act together (partially) determining the sense ofspace intended as an extension (distance).

GeoGraphy


a)

The space actant is given a distance resolution:

i.e. beyond a certain distance threshold, sources (vertices) are no moreaudible, i.e. signal is gated.

b)

Inside the audible radius the three main parameters correlated to distanceare:

1: amplitude; 2: high frequency energy; 3:reverberation

(simple distance cues).

GeoGraphy

Implementation of a “Generator + Distancer” module

GeoGraphy

Implementation of a “Generator + Distancer” module: a test

Sound Object (domestic percussion)

A sequence applying Distancer

(SA moving as in figure)

Without amplifier

First

Last emission

GeoGraphy

Il Gran Paese: memoria sull’attraversamento,

I-Ovest: da Nord a Sud (Sound objects families and trajectory)

GeoGraphy

Il Gran Paese: memoria sull’attraversamento,

II-Sud: da Ovest a Est (Sound objects families and trajectory)

GeoGraphy

Other distancers are possible --> Other spaces

Distancer II:

Filter: bandpass with a narrow bandwith (5 Herz).

distance controls the central frequency

the shorter the distance, the higher the sound;

Relation with decay time is inverted (the nearer the wetter)

GeoGraphy

Other distancers are possible --> Other spaces

GeoGraphy

Il Gran Paese:

memoria sull’attraversamento

Il Gran Paese V: Movimento a spirale

Distancer I

Il Gran Paese - Delle Bestie (V):

the same space as V-Movimento aspirale mapped to the space definedby the Distancer II

Same morphology + Differentcontrol function

Different acoulogical properties

GeoGraphy

Another space cue: Localization via displacement related to ears)

--> pan (distribution of energy on two channels of stereo)

GeoGraphy



Edges:{1: (1, 1, 0.5)}Actants:{1: [0.0]}

Two DSP mappingsusing panning

GeoGraphy



G.P: VI- Bustrofedico

GeoGraphy


a)

The space actant is given a distance resolution:

i.e. beyond a certain distance threshold, sources (vertices) are no moreaudible, i.e. signal is gated.

b)

Inside the audible radius the three main parameters correlated to distanceare:

1: amplitude; 2: high frequency energy; 3:reverberation

(simple distance cues).

c)

- pan is used to control signal panning (lateral-frontal displacement)

GeoGraphy

Implementation with Csound

Csound: general language for audio synthesis

MusicN family --> based on the orchestra/score paradigm

An audio rendering engine requiring two text files:

- an orchestra file: definition of instruments

- A score file: when and what instruments play

GeoGraphy

Implementation with Csound

ORCHESTRA SCORE

instr ID instrID attack duration other1 … otherndefendin

instr 1 1 0.0 0.35 4.3 0.4 0.35

func(param)

endin

GeoGraphy

Implementation with Csound: orchestra

instr 1; GENERATORar1 loscil 20000, 100, 1, 100 Read from file on HD

; DISTANCER; 1. Reverbarev reverb ar1, .4*p4 Reverbertate signalarr1 = ar1+arev1 Add to original

; 2. Filterkjexp = 10*p4/10; dist max=10 Calculate paramskexp = 10-kjexpklow = 21.5332*(2^kexp)at tone arr1, klow Filters signal with params

; 3. amplifieratamp = at1/p4 Scales proportionally to distance

; PANNERkpanr = (1+p5)/2 Uses lateral pankpanl = (1-kpanr)/2

outs (atamp1*kpanl)/2, (atamp2*kpanr)/2 Outs the results to file

endin

GeoGraphy

Implementation with Csound: score

i 1 0 5.29 8.51469318296 0.645942241466i 1 0.29 5.05 8.41915229963 0.653272420341i 3 0.34 5.98 11.2838397917 0.487422730342i 2 1.32 5.72 7.15130645407 0.559338356661i 1 2.04 5.29 7.86062694701 0.699689736847i 1 2.33 5.05 7.77134223356 0.707728450852i 3 2.38 5.98 10.5207880778 0.522774525951i 2 3.36 5.72 6.4375411455 0.621355251888i 1 4.08 5.29 7.25546855827 0.758048905571i 1 4.37 5.29 7.17414153595 0.766642248754i 1 4.66 5.29 7.09410838498 0.775291227809i 1 4.95 5.05 7.01541338768 0.783988012689i 3 5.0 5.98 9.57136934357 0.574630421476i 2 5.98 6.29 5.59264473314 0.715225119933i 2 7.27 5.72 5.21730455099 0.766679414803

GeoGraphy

Implementation with Csound phase vocoding opcodes

Phase vocoder is a analysis/resinthesis technique:

- results of Fourier analysis are stored in a data file

- Can be modified

- And used to resynthesize the signal

Possibilities:

- Independent time/pitch stretching

- Partial resynthesis (pvadd opcode)

GeoGraphy


- The general parameter “distance” controls the phase vocoderparameters.

- There is only one instrument in the orchestra

- Vertex index is passed as a p-field for the grain generator.

A sequencing program (Graphista!) generates the (very large) Csoundscore file according to the model, passing at least four parameters:

p4 (distance, idist),

p5 and p6 (right/left and frontward/backward displacement),

p7 (vertex index).

GeoGraphy


Distance controlsspectral richness andamplitude:

- number of bins

- grain duration

- amplitude

Note also:

Quadraphonic panning

GeoGraphy

Space

Considering one of the axis of the map space as frequency:

- the space actant displacement on that axis can be thought as a bandpass filtering

- if the distance has a threshold, bandwidth is represented exactly bythe diameter of the audible circle

Vertical axis considered asfrequency

Audible range diameter asbandwidth

GeoGraphy

Space

Sul grano (12 studiarmonici):

Each vertex represents aharmonic component ofa fundamental

4 trajectories x 3 ranges

2-513-b

2-513-c

8-513-b

f

GeoGraphy

Graph Placement

Graphs have geometric properties

(Group of) vertices can be distributed following:

- timbral spaces discussed in literature

- pitch spaces

- Post-tonal Set Theory (conglomerates of vertices can be thought assets)

Example: Density.

1. To enrich the spectral content of a musical object

- collapse several vertices in a single location

(i.e. all the vertices of a graph)

That location can consequently represent a very complex musical object.

GeoGraphy

Graph placement

Density, example

(edges omitted)

“Harmonic wood”: every conglomerate (vertices have not not exactly thesame location but share a small area) represent a series of grainswhich frequencies are harmonically- related (a complex tone).

- The fundamentals of all the conglomerates define a pitch set

- While moving through the Harmonic wood, distance controls relativerelevance of each conglomerate.

GeoGraphy

Example

Space actant

exploring

the “Harmonic wood”

from 1 to 150

sampled every 5 sec.

(edges omitted,

color represents

different graphs)

(Sopra l’archibugiar in valle, VII: ch’a la valle s’invola)

Low freq noise stripes

Sparse clicking dust

GraphMap presenting various distributions of vertices (i.e. grains):

3 vertical widestripes

3 orizontal densestripes

Set of dense blocks

Sparse dust

3 conglomerationswith identicalstructure

Trajectory exploringthe blocks

GeoGraphy

Graph placement

Density, example

(see before “conglomerations”)

(edges omitted)

(Sopra l’archibugiar in valle, V: tra i soffi)

The distribution is oriented from periphery to centre according to:

- Low/high frequency

- Low/high density

Core of the group: highest frequency region and highest densityregion (parameter linking).

GeoGraphy

Graph placement

Sopra l’archibugiar in valle,III, a lo scoppiar

Note low frequency densehorizontal stripes

GeoGraphy

Graph structure

Graph structure, example

Graph structure can contribute to stress hierarchical relationship in thegroup:

Star-structured graph: generates sequences of the form 1n1n…, thusstressing the importance of vertex 1.

GeoGraphy

Generating graphs

Graph structure, example

Graph as a Von Koch curve

(fractal iteration)

0 2

5 iterations

1250 vertices

(a circuit)

Example

5 iterations

1250 vertices

300 Graph actants

Control actant

exploring fractal borders

from I to F


(edges omitted,

colors represent

both iterations and

different grain sets)

Escursioni sulla frangia, II

Example

5 iterations

1250 vertices

300 graph actants

space actant

exploring fractal borders

from I to F


(edges omitted,

colors represent

both iterations and

different grain sets)

Escursioni sulla frangia, VI

GeoGraphy

Paesaggi su pergamena, I-V

- A generative algorithm for graph

- Generation information is stored in each vertex

- Generation information + distance/pan is used for DSP

To make both morphological and spatial information relevant

(DSP: Python)

GeoGraphy


Generative algorithm

Idea: a series of trees growing from fertile areas

Initialisation

In 10 regions sets of 9 vertices are distributed randomly

Regions: forests

vertices: tree (roots)

Vertices are “active”

Each vertex has associated a developmental direction randomly chosenamong N, S, W, E, NW, NE, SE, SE

A developmental radius (DR) is defined.

GeoGraphy



Iteration

While there is still 1 active vertex:

for each active vertex:

1. If there is a neighbour vertex (a vertex inside the DR):

1a. a new active vertex is generated inside the DR aroundthe vertex in the direction associated to the vertex

1b. an edge is generated from the active vertex to the newone.

2. The vertex become inactive

0 1 3

5 10 15

Some iterations (edges omitted)

GeoGraphy



Result

A series of trees start from each vertex developing in the root direction.

Little differences in the starting conditions create very different final results

The algorithm continues the iteration until no new vertices are generated.

GeoGraphy


Iterations with edges: 1 15

GeoGraphy



Result

End of the process: 105 iterations

3784 vertices

3693 edges

GeoGraphy



Actants

Graph actants start periodically from every root vertex

Each tree has an actant generating rate (0.1-1 second)

Graph actants die in the closing vertex of each tree

9x10 roots: 90 starting point:

There are always 90 parallel streams of grains

(to be filtered)

GeoGraphy


Iterations with edges: 1

GeoGraphy


DSP mapping

As before, 3 units:

Generator + Distancer + Pan

Pan: works as usual (lateral displacement trhrouhg distribution of thesignal)

GeoGraphy

Architecture: as before

GeoGraphy


DSP mapping

Generator

Starting material:

1. A set of audio samples found in the web

2. A diatonic mode (pitchList) = [0,2,3,5,6,8,10,11,13,15] is built on 5oHz fundamental

1. All the trees (10) of a forest uses the same sound sample

2. All the trees (10) of a forest use the same pitch of the mode

GeoGraphy


DSP mapping

Generator

Each vertex of a tree is characterized for 4 parameters:

Audio sample (10)

Pitch (10)

Tree (9 for each forest)

Iteration step

GeoGraphy


DSP mapping

Generator

3. Iteration step determines which DSP operation among a predefined setto apply to the sound sample (set by the forest)

4. Iteration step, tree and pitch act as parameter of the chosen DSPoperation

GeoGraphy


DSP mapping

Distancer

1. Duration of each sound event is proportional to distance

2. Amplitude of each sound event is inversely proportional to distance

3. Cut frequency of an averager (lopass filter) is inversely proportional todistance

GeoGraphy

Trajectories can be:

- explicitly defined by the composer

- generated algorithmically (e.g., brown motions).

The GraphMap is a space of “compossibilities”

- Different trajectories determines different strategies of exploration ofthe map space.

Two quasi-stochastic trajectories, exploring different regions ofthe same space (Sopra l’archibugiar in valle, I-VII)

(white/black dots = vertices; edges are not drawn)

GeoGraphy

Is it useful to generate algorithmically trajectories?

Too many variables? Too complex to be complex?

Random graph - with random trajectory (100 points)

GeoGraphy

Typically:

- Different algorithmic strategies for graph generation and placement

- Explicitly defined (“handcrafted”) trajectory

“The Percussion Room Frame” - Part 3

- The Listener does not know how, when, which percussion will play.

- But he is free to find an exploration strategy helping him tounderstand what is happening

There is no complexity without recognization of complexity

GeoGraphy

Conclusion

GeoGraphy

- The system features:

component I: organizes sound objects into a graph structure

component II: spatial level

- Sound organisation process is the design of a trajectory in the space,appropriately interpreted to control a number of parameters of audiblerelevance.

“It’s a complicated case, Maude. Lotta ins, lotta outs”

(Big Lebowski)

GEOGRAPHY: A TWO-COMPONENT SYSTEM FOR SOUND ORGANISATION

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