Bison Whistle
The bison whistle is a whistle made in the likeness of a white bison that Aang purchased for one copper piece in an Earth Kingdom town in The Waterbending Scroll. The whistle makes a sound too high to be heard by human ears and can be used to call animals. It is usually used to call Appa. It was also used to call every animal in Ba Sing Se in Tales of Ba Sing Se: The Tale of Aang.