Neville H. Fletcher
The Australian Aboriginal people developed three instruments: the didgeridu, the bullroarer, and the gum-leaf. Most well-known is the didgeridu, a simple wooden tube blown with the lips like a trumpet, which gains its sonic flexibility from controllable resonances of the player's vocal tract. The bullroarer is a simple wooden slat whirled in a circle on the end of a cord so that it rotates about its axis and produces a pulsating low pitched roar. The gum-leaf, as the name suggests, is a tree leaf, held against the lips and blown so as to act as a vibrating valve with "blown-open" configuration. Originally intended to imitate bird calls, the gum leaf can also be used to play tunes.