Virtual Music, Computer Synthesis of Musical Style.pdf

Preface

On November 8 and 9, 1997, as a part of a series of colloquia on computers and

creativity, Douglas Hofstadter, in conjunction with the Center for Computer Assisted

Research in the Humanities (CCARH) and Stanford University, presented a week-

end of papers, panels, concerts, and discussions centered around the works of the

Experiments in Musical Intelligence program. Presenters included Douglas Hof-

stadter, Eleanor Selfridge-Field, Bernard Greenberg, Steve Larson, Jonathan Berger,

Daniel Dennett, and myself. Virtual Music: Computer Synthesis of Musical Style

serves as a document to this colloquium, an extension of many of the thoughts pre-

sented there, and an annotated publication of sample musical output of the Experi-

ments in Musical Intelligence computer music composing program.

With the exception of the last two chapters, the presentation order of this book

closely follows that of the colloquium. Readers will note that both Doug Hofstadter

and I discuss the basic principles that Experiments in Musical Intelligence follows.

This apparent redundancy proved very e¨ective at the Stanford colloquium in that

Doug's informal view of the program e¨ectively serves as an introductory tutorial to

my more in-depth presentation.

Virtual Music: Computer Synthesis of Musical Style is divided into four main parts.

The ®rst part provides a background of Experiments in Musical Intelligence. It cites

precedents such as the eighteenth-century Musikalisches WÈrfelspiel and other

composing algorithms and presents a version of what I call The GameÐa reader

participation±style recognition test. This is followed by a general overview of Ex-

periments in Musical Intelligence as seen and heard through the eyes and ears

of Douglas Hofstadter, a renowned cognitive scientist and Pulitzer Prize±winning

author of GÈdel, Escher, Bach. I then respond to Doug's commentary which leads to

a description of the fundamental principles upon which the Experiments in Musical

Intelligence program operates.

The second part follows the composition of an Experiments in Musical Intelligence

work from the creation of a database to the completion of a new work in the style of

Mozart. This presentation includes, in sophisticated laypersons' terms, relatively

detailed explanations of how each step in the composing process contributes to the

®nal composition, with an example of ine¨ective as well as e¨ective output.

The third part provides perspectives and analyses of the Experiments in Musical

Intelligence program. These scholarly commentaries include analyses, critical evalu-

ation, and relevant history and documentation, as appropriate. These chapters also

discuss the implications of the program's compositions. The scholars include Eleanor

Selfridge-Field (musicologist, associate director of the Center for Computer Assisted

Research in the Humanities at Stanford University), Bernard Greenberg ( Bach

scholar and co-inventor of the Symbolics Lisp machine), Steve Larson (music theo-

viii

Preface

rist), Jonathan Berger (noted composer and theorist), Daniel Dennett (cognitive

scientist and author of Darwin's Dangerous Idea), and Douglas Hofstadter.

The fourth part provides my response to the commentaries presented in the third

part along with thoughts on a variety of implications I see as a result of my work

with Experiments in Musical Intelligence. These implications include re¯ections on

arti®cial intelligence, music cognition, aesthetics, intention, and the future of both

Experiments in Musical Intelligence and, indirectly, the use of computers in the new

millennium.

Appendix A includes the music of the databases used to create a new Mozart-style

movement which appears in appendix B. Appendix C contains a rejected Mozart-

style movement, as discussed in chapter 10. Appendix D provides extended musical

examples referred to and discussed in Virtual Music. The music covers styles from a

four-hundred-year span of classical music history and includes such composers as

Scarlatti, Bach, Mozart, Beethoven, Schubert, Chopin, Rachmanino¨, Proko®ev,

Joplin, BartÂ k, and others. Each music example is preceded by a brief documentation

of its composition or thoughts on its aesthetic value. Appendix E presents the key to

The Game in chapter 1 (see ®gures 1.11±1.13).

I have written Virtual Music using nontechnical terminology and in a style which I

feel will appeal to the layperson with an interest in classical music, as well as to

individuals knowledgeable about arti®cial intelligence. Since many of the examples

are musical scores, an ability to read music will be bene®cial. Those unable to play

these examples on the piano will ®nd the music available on the accompanying

compact disk or on commercially available CDs of Experiments in Musical Intelli-

gence's music: Bach by Design, Classical Music Composed by Computer, and Virtual

Mozart (Cope 1994, 1997b, 1999).

Like most computer applications, Experiments in Musical Intelligence has had

many incarnations. The program has been revised continually over many years.

Therefore, the music from the mid-1980s was created by a substantially di¨erent

program from the one that exists now. There are de®nite commonalities among the

various forms of the program, and I tend to emphasize these features in my writings

and discussions. I mention these versions for several reasons. First, individuals who

have followed my work through various writings can become confused by the varia-

tions in the descriptions of Experiments in Musical Intelligence they encounter. While

I try not to contradict earlier publications, I tend to emphasize important, newer

aspects of the program in current writings, aspects which may not have even existed

in earlier versions. Readers should be aware of the distinctions of the various incar-

nations of the program. Second, I do not want listeners of Experiments in Musical

Intelligence's music to be searching for compositional processes which, by virtue of

Preface

the period in which they were created, do not exist. Finally, I mention these versional

di¨erences in Experiments in Musical Intelligence because the approach I take in

describing the program in this book is a current version, which has only existed in this

form since about 1993. Most of the Experiments in Musical Intelligence program's

output, therefore, cannot be understood to have been composed using all of the pro-

cesses described in this book. However, the works composed speci®cally for this book

in appendixes B and C were created using this version.

I wish to thank the many individuals who have contributed so very much to this

body of work, particularly Douglas Hofstadter, who created the series of colloquia

on computers and creativity at Stanford University in 1997 which led to the creation

of this book. I also wish to thank the Center for Computer Assisted Research in the

Humanities, particularly Eleanor Selfridge-Field, Don Anthony, and Walter Hewlett.

Without the moral support and advice of colleagues such as these, this book could

not have been completed.

The CD

The CD which accompanies this book contains two sets of music. The ®rst set con-

tains some of the musical examples of Virtual Music: Computer Synthesis of Musical

Style. Each example is named and numbered according to the text for easy refer-

ence. The second set contains performances of many of the works presented in the

appendixes of Virtual Music, especially those not already available on commercial

recordings.

The music of both of these sets is performed here by a computer algorithm I

developed called, simply, Performance. Like Experiments in Musical Intelligence,

Performance relies on a database of already performed music for analysis which it

then uses as a model. Performance does not use recombinancy, however, but rather

uses its analyses as temporally ¯exible templates. Performance alters only the rhythm,

articulation, and dynamics of the works it performs.

Music on the CD

Figures

Track

1.1±4

1.7±9

1.11a

1.11b

1.11c

1.11d

1.12a

1.12b

1.12c

1.12d

1.13a

1.13b

1.13c

1.13d

4.1±2

4.5±7

4.9±13

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