Sumer Is Icumen In is the oldest known counterpoint song, written 1240.
Sumer Is Icumen In
Sumer is a-coming in,
Loudly sing, cuckoo!
Groweth seed and bloweth mead
And springeth wood anew.
Sing, cuckoo!
Sing, cuckoo! Sing, cuckoo! Sing, cuckoo! 
KOMOS
Lumina Vocal Ensemble
Randy Tandy
Hummelpiper
Circulus
Sleepytime Gorilla Museum
The Sea Nymphs
Nat King Cole
