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Virtual Music: Preface - 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-
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
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, Bart 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
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
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
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