@patchlore It's used by a people who live on the back of these large 4 legged creatures, high up in the clouds. The creatures and the residents of its back whistle to each other over long distances.
The poem is sung by one of its inhabitants who fell from the back of the Ilk and climbs a mountain and find someone sleeping there, and they wait for the person to wake.
@patchlore The notes of the whistle language is Solresol.
http://wiki.xxiivv.com/site/solresol.html