Robotics Reference
In-Depth Information
those bars that are of the same functional type as the one that originally
followed what is now the first bar. It also takes into account that the
melody of this next bar may have a strong tendency towards a certain
continuation, as might be determined by a Markov chain database, and
so it looks for a next bar that fits this preference of the melody. This
process continues until a full musical phrase has been generated, with
a structure that adheres to the style being imitated and with a signa-
ture in the correct place within the phrase. The composer module also
transposes all of the snippets into the same key and adapts the individ-
ual voices (musical instruments) to the appropriate range. This prevents
melodies and harmonies from overlapping in range or from becoming
too distant.
Using this method in order to recombine musical elements would be
too simple an approach, without the use of signatures, to enable the sys-
tem to describe an ordering of the melodic and harmonic material that
conformed to the constraints of the composer's style. The result would
perhaps be a piece of Mozart that is recognizable as a symphony but
rather a boring one. The pattern matcher is essential in creating works
that sound typical of the intended composer, because the signatures iden-
tified by the pattern matcher provide the composition with sequences of
notes that fit the newly generated structure, while at the same time in-
cluding recurring motifs from the composer's oeuvre, sequences of notes
that typify that composer.
Ironically, although EMI sometimes produces music as sublime as
Mozart's, the program cannot tell the difference between a work of genius
and a badly written nursery song, so for the time being it is left to Cope
to decide which pieces of EMI's music are good enough to let out of his
studio. Most of it goes straight into the waste bin once Cope has heard
it. The small minority of pieces that survive are those that Cope finds
pleasing, a judgment that EMI can not yet make for itself. Eventually
EMI will probably be endowed with an accurate evaluation function that
can measure both the musical quality and the level of originality of a new
work, whereupon it will be able to make the decision itself as to which
works to discard and which to present to its operator.
How Computers Create Visual Art
The beginnings of computer art parallelled the early days of computers,
when artists used to create their work on oscilloscope displays using raster
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