Computational Creativity and Music - Computational Creativity Research: Towards Creative Machines - page 316

7 3 +6 7 7 3

3 r 5 3 3 r

r 3 r r

-1 1 -1

1 -1 1

5 -1 5

M It M M

Mm 7 Mm 7

Fig. 15.12 The same-sounding major-minor seventh chord resolving first to a major triad missing
fifth, then as an Italian augmented sixth chord to a M triad missing fifth, and then a respelled Italian
augmented sixth chord to a different M

sub-program that extracts the rules in themanner described earlier in this chapter. And
the last component uses those rules to produce output. With the examples presented
here, any good programmer could code such a program in a very short time.

15.3.3 Counterpoint

Even given these arguments for machine creativity, however, I here present more
complex examples, one created by a human and the other by a computer not unlike that
just described but having greater degrees of analytical and compositional constraints
than those previously described.
Composing Baroque fugues requires at least as many rules as chess and
language, probably more so considering that not only does the form itself have rules
regarding entrance of the theme and keys, but that these rules must fit within the
strict conditions of triadic harmonies and tonal voice-leading involving consonance
and dissonance as well as contrary and oblique voice motions. Rules once again,
therefore, are particularly important ingredients to the creative engineering of a good
result. Interestingly, Bach ends his exposition as required on a tonic B-minor triad
at the end of his exposition (measure 21 of Fig. 15.13 a), while the Emmy example
ends its exposition on a B-major triad in the middle of its measure 15 (Fig. 15.13 b).
Is this creativity, or simply a mistake by the program? Possibly it's an interesting
correlation with Bach's immediate (measure 22) reference to B-major as well, since
the rules used for creating Fig. 15.13 b included the Bach in Fig. 15.13 a. Given the
forward and backward chaining of the Markovian processes described previously,
the latter makes perfectly good sense.
All of the examples in the figures of this chapter can be heard from files pre-
sented on my website at https://arts.ucsc.edu/faculty/cope/new.html . My inclusion
of clearly more elegant examples here may seem unfair to those who would like to