The first known canon of European art music, now in the British Museum in London, is preserved in a thirteenth-century manusript from the English abbey in Reading: This is the so-called "summer canon", whose verses greet the advent of summer. An accompanying note elucidates the artistic layer-like construction of the sound structure: a two-voice foundation of bell-like, swinging pendulum tones supports an upper structure of four voices which enter at equal time intervals. The note terms the cano...