Undiscovered Bach? No, a Computer Wrote It (1997)
nytimes.com
nytimes.com
Though he seems only indirectly involved (the OM book's preface), OpenMusic [1], seems to contain most of his ideas of how a language should tackle those problems. OM is actively developed, latest release was 2017-04-27, so far as I can see.
[0] http://artsites.ucsc.edu/faculty/cope/bibliography_page_2.ht...