Johann Christoph Oley (1738 - 1789) was a German organist and composer. In 1755 he became organist of the church in Bernburg, but moved to the church of St Stephan in neighbouring Aschersleben in January 1762 because of its superior organ. At least 77 works for organ solo by his hand survive. The most interesting combine his fondness for strict canon with passages in the more expressive style. "Freu dich sehr, O meine Seele" is a great example. Canon (mostly) on the chorale between soprano, tenor and bass, and one voice (alto) moving freely in between.
My first impression was "what a boring piece". But after playing through it a few times I quickly learned to enjoy that free moving alto voice. What a nice combination of strict canon and something frivolous in between.