In this riddle, a Tibetan flute is compared to a tree with nine holes.  Historically, Tibetan flutes came in two varieties: flutes played by blowing straight down into the flute, and flutes played by blowing transversely across a hole.  While distinctive and used in different kinds of music, Tibetan flutes of both varieties were generally made of wood or bamboo and featured nine holes on their top sides.  Interestingly, in Tibetan tradition, the bodies of humans and other animals are said to have nine holes (eyes, ears, nose, mouth, urethra, and anus). As such, when the riddle asks, “What is a tree with nine holes?” the question lends the tree an animalistic quality. Instead, the answer is a wooden flute.