https://en.wikipedia.org/wiki/Sumer_Is_Icumen_In
Modified by Robert Ford
“Sumer Is Icumen In” (also called the Summer Canon and the Cuckoo Song) is a medieval English round or rota of the mid-13th century  song  – – a celebration of  summer.
The title translates approximately to “Summer Has Come In” or “Summer Has Arrived”.  The composer’s identity is unknown.    The British Library now retains this manuscript (Millett 2003a).

In this work, you  will first hear  a “ground”  in the lower voices – repeated phrases  which support the  round  sung above. One person begins at the same time as those who sing the ground. When he comes to the first note after the cross  (see  figure below) which marks the end of the first bar, another singer is to begin, and the others follow..

“Sumer Is Icumen In” in modern notation:

  Note he difference between the Middle English and the Modern  English language below.