Roundabout

https://commons.wikimedia.org/wiki/File:Stuber-Musique.jpg

Alsatian pastor J.G. Stuber composed this puzzle canon in the late 18th century.

“It was always a great delight to me, in riding my horse from one village to another, to hear in the fields and among the heights the melodies which I had taught,” he wrote. “I could often distinguish very beautiful and harmonious voices.”