The grung are trained to use this new musical instrument. This is a hollow tube with holes cut throughout, much like a flute. You can play music with it for entertainment, but the grung also swing it about by a sturdy cord (attached) to create a sound recognizable by other grung, so they know each other’s approximate location. Additionally, grung that know Thieves’ Cant can use a whistle stick in this manner to communicate over distance.