Interlude. Why Machines Learn on Bach

Nearly every machine that seriously tried to play or compose sat down to Bach sooner or later. In 1968 Wendy Carlos proved that Moog’s synthesizer was fit to be a musical instrument using pieces by Bach, which she recorded note by note. In the 1972 Solaris, through the hum and shimmer Eduard Artemyev drew out of the ANS, Bach’s chorale prelude in F minor breaks through. In the eighties and nineties David Cope fed his program Emmy on Bach chorales until it had written five thousand of them and listeners in Oregon mistook its piece for Bach’s.

The reason is thoroughly practical. Bach comes with an almost ready-made training set. His four-part chorales, Lutheran hymn tunes he harmonised for his parishioners, are short and written for the same voices, soprano, alto, tenor and bass, by the same rules of voice leading, so they are easy to lay out in a table and count. It wasn’t Bach himself who collected them for print. From 1777 the publishers were being courted by Johann Philipp Kirnberger, a Berlin theorist who had studied with Bach in his youth and twenty years earlier had published a dice game for composing minuets. Kirnberger died in 1783 without seeing the book, and the job of bringing it out fell to the composer’s son Carl Philipp Emanuel, who in 1784–1787 printed the chorales in four volumes with the Leipzig publisher Breitkopf. Since number 283 appears in them twice, the chorales came to three hundred and seventy-one, and they still live under that number, first in harmony textbooks and now in datasets for neural networks.