Leaf whistling is an ancient Hawaiian practice of blowing into a leaf to make it vibrate in different pitches. Hawaiians developed the practice by using leaves from the ti plant and blowing into their hands. Leaf whistling works much the same way as reed instruments such as clarinets and saxophones. With reed instruments, the vibration of the reed from your breath creates the sound. You want to create an air chamber with your hands for the leaf vibrations to resonate.
Place the leaf between the inner thumbs of the right and left hand.
Cup your hands to form an air chamber.
Stretch the leaf as tightly as possible from the top and bottom of your thumbs.
Blow into the middle of the leaf and make it vibrate in the air chamber.