following the program does not serve to enlighten one as to why this
particular discovery popped out, then perhaps one should begin to sepa-
rate the program's "mind" from that of its programmer. The human gets
credit for having invented the program, but not for having had inside his
own head the ideas produced by the program. In such cases, the human
can be referred to as the "meta-author"-the author of the author of the
result, and the program as the (just plain) author.
In the particular case of Gelernter and his geometry machine, while
Gelernter probably would not have rediscovered Pappus' proof, still the
mechanisms which generated that proof were sufficiently close to the
surface of the program that one hesitates to call the program a geometer in
its own right. If it had kept on astonishing people by coming up with
ingenious new proofs over and over again, each of which seemed to be
based on a fresh spark of genius rather than on some standard method,
then one would have no qualms about calling the program a geometer-but
this did not happen.
Who Composes Computer Music?
The distinction between author and meta-author is sharply pointed up in
the case of computer composition of music. There are various levels of
autonomy which a program may seem to have in the act of composition.
One level is illustrated by a piece whose "meta-author" was Max Mathews of
Bell Laboratories. He fed in the scores of the two marches "When Johnny
Comes Marching Home" and "The British Grenadiers", and instructed the
computer to make a new score--one which starts out as "Johnny", but
slowly merges into "Grenadiers". Halfway through the piece, "Johnny" is
totally gone, and one hears "Grenadiers" by itself ... Then the process is
reversed, and the piece finishes with "Johnny", as it began. In Mathews'
own words, this is
... a nauseating musical experience but one not without interest, particularly
in the rhythmic conversions. "The Grenadiers" is written in 2/4 time in the
key of F major. "Johnny" is written in 6/8 time in the key of E minor. The
change from 2/4 to 6/8 time can be clearly appreciated, yet would be quite
difficult for a human musician to play. The modulation from the key of F
major to E minor, which involves a change of two notes in the scale, is jarring,
and a smaller transition would undoubtedly have been a better choice.^12The resulting piece has a somewhat droll quality to it, though in spots it is
turgid and confused.
Is the computer composing? The question is best unasked, but it cannot be
completely ignored. An answer is difficult to provide. The algorithms are
deterministic, simple, and understandable. No complicated or hard-to-
understand computations are involved; no "learning" programs are used; no
random processes occur; the machine functions in a perfectly mechanical and
straightforward manner. However, the result is sequences of sound that are
unplanned in fine detail by the composer, even though the over-all structureArtificial Intelligence: Retrospects 607