The main theme of this issue of Organised Sound is algorithmic compostion,one which we have featured before, and yet the flavour of the current issue is verydifferent. It perhaps says something of the richness and the variety of the topic that it canelicit such different responses. Perhaps many of us are still not clear exactly what algorithmiccomposition is, and the vagueness of the definition itself contributes to a broad rangeof responses.

To begin with, I would like to cite the influence, both direct and indirect, of the following disciplines on my personal: research: philosophical reflection, linguistics and physics. I will do this briefly sketching the fusion of these disciplines, not strictly with my music and the role it plays as the foundation of a personal aesthetic.

This paper outlines some of the technical and aesthetic issues arising frommy works which involve computer technology directly in live performance. Aprocess of experimentation in algorithmic composition is described,particularly in relation to aspects of form and ways of automating musicalprocesses at various structural levels. Three works are then described:Kendhang is a work in which a dancer influences the output of asimple algorithmic music system based on interpolation;Or is an instrumental trio which uses realtime sound granulation;and Vug extends this realtime granulation and applies it to a soloclarinet line. An exploration of both the distinctions and similaritiesbetween these works is used to develop a general approach to the integrationof computer-based algorithmic systems with live performance. This approachemphasises the need for efficient use of technological resources in orderto convey expressive content accurately.

This paper describes the ideas and methods that led to the writing of analgorithmic composition NTrope Suite. This piece, for solorecorders and voice, was generated by ‘mixing’ works bydifferent composers from different eras. The idea behind the work was toexamine random generation procedures that could maintain stylisticproperties typical to the reference works. The interesting property ofthis method is that it implements a sort of ‘statisticallearning’, that optimally preserves the properties of the referencepieces and also properly ‘generalises’ them so as to create anew valid work. The musical result is very coherent, maintaining bothstylistic resemblance to the reference music and exhibiting some surprisingoriginality as well. Theoretically, the resulting piece is closest to thereference works in terms of mutual entropy. The algorithm and itstheoretical significance are discussed in the paper.

Palatal Sound is a model of vocal tract articulation influenced byphysiologic and acoustic analysis of the voice. Specifically, the termarticulation refers to all movement within the vocal tract that resultsin open, filter-like sonorities, as well as in turbulent to absoluteairflow modification. This model presents a complete mapping of placewithin the vocal tract that features flexibility across different vocaltract sizes and proportions. The principles behind this comprehensivemapping of acoustic and physical sound production techniques should notbe foreign to those persons who create, combine, design, model or researchsound. Therefore, this model might suggest avenues of sound explorationregardless of media or application. This text first presents a briefoverview of the current trends of oral modification using vowels, followedby an introduction to and acoustic analyses of the comprehensive vocaltract model as applied to open-like sonorities. This model is then expandedthrough the presentation of other methods of open-like behaviours. Followingthe discussion of open sonorities, turbulent-like behaviours are discussedby first identifying the use of language-based fricatives and stops. Afterthis (re-)exposition, the comprehensive model is applied to turbulentstructures through examples and acoustic analyses. Finally, these turbulentmethods are completed by additional, complementary methods of vocal tractturbulence. The intentions of this paper are: (i) to document this modelclearly, (ii) to identify differences between speech and song articulatorybehaviour and that of this comprehensive model with the aid of selectedacoustic analyses, (iii) to suggest that this model renders valuablescientific information about the limits of vocal tract physiology, and(iv) to propose the practical use of this model by composers andperformers.

KYKLOS, an algorithmic composition program, is presented here. Itgeneralises musical scales for use in composition as well as inperformance. The sonic output of the system is referred to aspolymodal music since it consists of four independent voicesplaying ‘synthetic modes’. KYKLOS is suitable forcomputer-assisted composition because it generates MIDI files which can bealtered later by the composer. It can equally well be used in liveperformance for dynamic modification of parameters enabling realtimemusical control.

For a system to be able to generate realtime accompaniment topreviously unknown songs, it must predict their harmonic development,i.e. the chords to be played. We claim that such a system must combinelong-term experience, to identify typical chord sequences (e.g. II–Vand II–V–I), with ‘on-the-fly’ adaptation totrack-recurrent structures (e.g. choruses and refrains) of the particularsong being played. We have implemented a prediction system using a neuralnetwork model that encompasses prior knowledge about typical chordsequences. The results achieved are very encouraging, and rather betterthan those reported in the literature. However, our predictor could notadapt its behaviour to the idiosyncrasies of each song, since onlinelearning is difficult in neural networks. In this paper, we propose anextension to our previous work by the inclusion of a rule-based sequencetracker, which detects recurrent chord sequences while the song is beingperformed. We show that this hybrid model, which combines a neural network predictor with a rule-based sequence tracker, improves thesystem's performance.

This paper presents an end-user interface that allows realtime parametriccontrol of sound events resulting in an interactive environment, in whichevolutionary computation is applied to algorithmic composition. Theresulting system, Vox Populi, uses genetic algorithms to generate andevaluate a sequence of chords played as MIDI data. Harmonic, tonal andvoice range fitness are used to control musical features. Based on theordering of consonance of musical intervals, the notion of approximatinga sequence of notes to its harmonically compatible note or tonal centreis used. This method employs fuzzy formalism and is posited as anoptimisation approach based on factors relevant to hearing music.

A computer-assisted composition tool for investigating the application ofevolutionary techniques in the composition of music is presented. The natureof such an application is examined in terms of defining the possiblemechanisms that provide a means for automated creativity. These mechanismstake inspiration from processes found in Darwinian-based evolution theory,genetic algorithm theory and similar aesthetically based uses of a geneticsearch heuristic in the visual arts. A formal model of ‘musicalevolution’ is proposed, with particular emphasis placed on the waysin which a genetic algorithm can be used to effectively manipulate avariety of compositional structures within a hierarchical and generativegrammar-based model of musical composition. The result is a prototypeWindows MIDI application called GeNotator that allows composers toexperiment with a range of musical structures by interactively‘evolving’ them through a familiar and comprehensive graphicaluser interface.