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       M U S I C          T H E O R Y         O N L I N E

                     A Publication of the
                   Society for Music Theory
          Copyright (c) 1994 Society for Music Theory
| Volume 0, Number 6      January, 1994    ISSN:  1067-3040   |

  All queries to: mto-editor@husc.harvard.edu
AUTHOR:  Smoliar, Stephen W.
TITLE:  Computers Compose Music, But Do We Listen?
KEYWORDS:  music composition, EMI, artificial intelligence, ATN

Stephen W. Smoliar
National University of Singapore
Institute of Systems Science
Heng Mui Keng Terrace
Kent Ridge, SINGAPORE  0511

ABSTRACT: This is an examination of the current state of the
art in the computer composition of music.  David Cope's EMI
(Experiments in Music Intelligence) project is examined as a
representative of this state of the art.  Both its assets
and its liabilities are considered.  However, the conclusion
is that the matter of whether or not a computer will ever be
a successful composer may not be that appropriate a
question.  Music is ``in the ear of the listener;" and
audiences listen to *performances* rather than
*compositions*.  The quality of performance often overrides
whether what is being performed has come from a struggling
genius, a commercial hack, chance decisions, or even a
computer program.

[0] NOTE: This paper has been reproduced with permission
from World Scientific from their volume MULTIMEDIA MODELING.


[1] Members of the IEEE Computer Society may recall that the
July 1991 issue of their monthly magazine, *Computer*, was a
special issue devoted to the topic of ``Computer-Generated
Music."  There has long been a fascination with mechanical
means for generating original musical compositions.  Indeed,
that fascination preceded the invention of the computer
itself by several centuries.(1)


1.  Hiller, L. A. and Isaacson, L. M.  *Experimental Music:
Composition with an Electronic Computer*, New York:
McGraw-Hill (1959).


[2] Of the articles which appeared in this special issue,
the one which probably best characterizes the current state
of the art is ``Recombinant Music: Using the Computer to
Explore Musical Style," by David Cope.(2) The topic of the
article is a component of a more general project called
Experiments in Musical Intelligence (EMI).  Cope provides an
excellent summary of the fascinating behavior of this
component in his introduction:

This EMI subprogram . . . separates and analyzes
musical pitches and durations and then mixes and
recombines the patterns of those pitches and
durations so that, while each new composition is
different, it substantially conforms to the style
of the original.  The new works generally inherit
aspects of the style of the period and, to a
lesser degree, the style of the composer of the
recombined works.  Called *recombinant music*,
this is not just a parlor game but a serious
attempt to understand how listeners recognize the
style of a composer or period, one of the more
elusive and difficult to describe musical


2.  Cope, D.  "Recombinant Music: Using the Computer to
Explore Musical Style," *Computer* 24 (7) (1991): 22-28.


[3] Cope's claim is as fascinating as it is bold.  His
article leads the reader through an exercise in the
synthesis of a piano sonata in the style of Wolfgang Amadeus
Mozart.  In an earlier paper(3) he demonstrated that his
technique works for not only Mozart but also Giovanni
Pierluigi da Palestrina, Johann Sebastian Bach, Tomaso
Albinoni, Frederick Chopin, Bela Bartok, Igor Stravinsky,
and Scott Joplin.  These are extensive efforts.  If we are
to consider whether or not we are on the threshold of the
age of computer composers, we need to examine both the
assets and the liabilities of Cope's EMI system.  Having
done so, we may then be able to ask whether artificial
intelligence has now solved the problem of turning a
computer into a successful composer.


3.  Cope, op. cit.



[4] Perhaps the most important thing about Cope's results is
that, at first hearing, they do a good job of *sounding*
convincing.  One can play the "EMI-Mozart sonata movement"
illustrated in his *Computer* article and be reasonably
fooled into taking it for "real" Mozart.  Serious Mozart
scholars are less likely to be fooled, but even *they* may
have to listen for a bit before identifying what they hear
as an imitation.  If nothing else, Cope may have latched on
to getting a computer to perform an important exercise in
the study of "free composition:" the task of using an
existing composition as a model which guides the structuring
of a new one.(4)


4.  Schoenberg, A.  *Models for Beginners in Composition*,
New York: Schirmer (1943).


[5] Such a model-based approach is important because it
takes the computer away from the ultimately misguided
approach to music composition as a process of putting notes
together.(5) Composition operates at a larger granularity,
and Cope's recombinant music may be regarded as a hypothesis
of a more viable grain size.  Just *how* those grains are
determined--whether they are products of pattern matching
algorithms which lie at the heart of EMI's operation or of
Cope's own skill at musical analysis--is not made entirely
clear; but the results are impressive enough to justify
taking his thesis seriously.


5.  Smoliar, S. W.  "Algorithms for Musical Composition: A
Question of Granularity," *Computer* 24 (7) (1991): 54-56.


[6] However, the possibility that Cope's own skill may
figure in EMI's results may, itself, be one of the system's
assets.  Cope's work may be distinguished from many other
results in computer-generated music by the fact that Cope,
himself, is a serious composer.  This makes EMI a system
which is based on *practice* as much as *theory*, if not
more so.  In other words the judgments exercised by Cope in
developing EMI may very well have more to do with how
practical experience guides his decisions than with any
attempts at theoretical models which dictate how decisions
*should* be made.


[7] Nevertheless, it is important to observe that the extent
to which EMI is convincing as a composer in its own right is
superficial, in the literal sense of the word.  In other
words the decisions which EMI makes in composing a piece of
music are all concentrated on the surface structure.
However, much of music theory has been concerned with the
question of whether or not music has a "deep structure,"
such as that which Chomsky claims is in natural language.(6)
Cope is well aware of the importance of deep structure in
both natural language and music.  Indeed, much of his
success is based on the power of the augmented transition
network (ATN) to handle both the analysis and synthesis of
natural language syntactic structures.(7) The heart of
Cope's work involves adapting the ATN so that it may
accommodate the synthesis of *musical* structures.(8)


6.  Chomsky, A. N.  "Language: Chomsky's Theory," in *The
Oxford Companion to the Mind*, Gregory, R. L., editor, New
York: Oxford University Press (1987): 419-421.

7.  Woods, W. A.  "Transition Network Grammars for Natural
Language Analysis," *Communications of the ACM* 13 (10)
(1970): 591-606.

8.  Cope, op. cit.


[8] At this point, however, one can raise the question as to
just *who* is doing the composing.  Ultimately, the success
of the computer at "synthesizing" Mozart or Joplin depends
on Cope's success at designing an ATN which controls that
synthesis.  This technique is not that different from the
one Mozart engaged for his own "Dice Composer," a toy which
enabled his contemporaries to compose simple dances without
any prior knowledge of music just by rolling a pair of
dice.(9) I recently demonstrated that this toy was basically
a very well designed random sentence generator.(10)

Mozart's Dice Composer, for example, generated (to
use the terminology of computational linguistics)
random sentences by selecting productions from a
simple context-free grammar.  Each of the terminal
symbols in this case was an entire measure of
keyboard music.  Each measure of the score, in
turn, corresponded to 11 productions, each of
which filled in that measure with one of those
terminals.  The bulk of Mozart's work with the
Dice Composer was to make sure that the terminals
chosen for any given measure were interchangeable.

It would thus be fair to say that the *real* composer of
anything produced by the Dice Composer is Mozart, himself,
rather than whoever happens to be tossing the dice.  By
similar reasoning, then, in designing specifications with
ATN representations, Cope is the one doing the composing,
even if EMI is actually "generating the output."


9.  Mozart, W. A.  *The Dice Composer*, New York: Guild
Publications of Art and Music (1941).

10.  Smoliar, op. cit.


[9] Of course Mozart never drew upon use of the Dice
Composer for his *own* compositions.  One may assume that he
felt that music it produced was "not good enough" for his
personal standards.  Indeed, he used his standards for what
it meant to be "not good enough" as a basis for another
composition, his K. 522 sextet, subtitled *Ein Musikalischer
Spass* (a musical joke).(11)  This composition serves as a 
sort of *catalogue raisonne* of the sorts of faulty devices 
one could find in the work of mediocre (or poorer) composers 
of Mozart's day.  Such composers would often have a few good 
ideas but simply never got the details correct, and Mozart was 
capable of picking out examples of such inattention as a subject 
for lampoon.


11.  Apel, W.  "Musikalischer Spass, Ein," in *Harvard
Dictionary of Music*, Apel, W., editor, Cambridge: Harvard
University Press (1969): 560.


[10] This is not to say that Cope's work is a joke.
Nevertheless, it in unclear just how seriously an
experienced listening ear may be expected to react.
Certainly, it will not react to the Mozart examples as if it
has just encountered a previously undiscovered Mozart
composition.  More likely, it will respond with an uneasy
sense of familiarity, as if it had been *reminded* of Mozart
but then recognized at least one spanner in the works which
caused the result to be "not quite right."

[11] Of course it is important to remember that the first
letter of EMI stands for "Experiments."  In the world of
science, not all experiments succeed; but we assume we can
learn something even if the outcome is not successful.  Can
we learn anything from the results of Cope's experiments?

[12] One thing we may learn is that, whether or not music
*has* a deep structure, much of our response, as
individuals, is to surface features.  Thus, we can pick up
on surface cues and start to follow through with them, even
if the music does not follow through in the same way.  This
is particularly the case if the music is *performed* with
the appropriate air of seriousness.  Cope has been fortunate
enough to have his work performed by skilled
instrumentalists and singers participating in the Santa Cruz
Baroque Festival.  Hearing these results performed with the
same seriousness of purpose which one would expect for a
performance of Palestrina or Bach quickly dispels any notion
that this is just another variation on a Mozart-type musical
joke.  Because the *performers* are not the village amateurs
which Mozart chose to ridicule, we assume that the
*composer* is no less mediocre.  Ultimately, whether or not
the results are laughable depends upon whether or not they
receive very loving performances in a very convincing
manner.  Whether or not we come away any the wiser about
"Musical Intelligence" or the stylistic characteristics of
Mozart or Joplin may ultimately be beside the point.


[13] Erik Satie was a key forerunner of the avant garde
approach to musical composition which developed at the
beginning of this century.  There is a story that Satie was
once (if not many times) asked if he felt that the sorts of
things he did were *really* music.  It is said that Satie's
favorite answer to this question was: "Music is what happens
at concerts."  This seems to capture a key element of what
makes output from EMI "work."  Whether or not it was music
when it came out of the computer, it was *certainly* music
when it happened at the Santa Cruz Bach Festival!

[14] Thus, the *real* lesson to be learned is that, in
matters of music, practice is more important than theory.
Music is what musicians do at concerts, and practice has
more to do with *performing behavior* than with writing
scores.  Performing behavior remains a great mystery to us,
but it has tremendous power.  Skilled actors are capable of
picking up a telephone directory and reading aloud from it
with the same command of emotional manipulation they can
apply to Shakespeare.  This does not mean that a telephone
directory is "great literature;" but it *does* mean that a
good enough actor can fool a willing audience into taking it
as such!  This is because we, as audiences, do not listen to
compositions; we listen to the *performances*.  Composition
is simply the armature which is then fleshed out by

[15] For many centuries this approach to music behavior was
pretty much taken for granted.  It has only been in the last
century or two that the composer has begun to assume the
role of "significant individual" in his own right.  In
today's world of competitions and grants, the situation has
become even more exacerbated.  The consequence is that we
seem to be losing sight of the behavior side of the story,
particularly the significance of the behavior of the
performer.  Yet it is that performer behavior which
ultimately determines whether or not we, as audience, decide
to devote enough attention to listen, regardless of whether
what is performed has come from a struggling genius, a
commercial hack, chance decisions, or even a computer


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