sorry, but: caveat city.
I studied with Dr. Cope here:
http://arts.ucsc.edu/programs/WACM
Emmy is not the same as Emily Howell; the Emmy Vivaldi was composed by a simpler program called EMI.
In either case, iirc, the music's composed by probabilistically combining key-signature-normalized snippets of existing compositions. EMI mostly just took the works of one composer and created a new work in that composer's style by Frankenstein-remixing snippets of the composer's actual works. Emily Howell, iirc, does the same, but uses multiple composers and/or original snippets by Dr. Cope.
btw: feed EMI Beethoven, and "she" produces Mozart. i.e., when probabilistically combining several key-signature-normalized Beethoven snippets, some of the results were identical to larger snippets of Mozart (who was, as you may have guessed, a big Beethoven fan).
also btw: Beethoven wrote algorithmic compositions for people to perform as a parlor game, with dice.
also also btw: my own drum-and-bass Ruby project from years ago will generate an infinite amount of new jungle riddims all day for free:
https://github.com/gilesbowkett/archaeopteryx