Introduce : Hang drum consists of two metal hemispheres joined together (each hemisphere has overlapping metal layers), one hemisphere has the upper surface called Ding, the other hemisphere is called Gu. Ding face contains 8 nodules forming "sound ring", this ring surrounds a knob in the center called Ding (like the knob of a gong) .... On Gu's face there is a sound hole in the middle called Gu. Gu's face can play like Udu or use to tune Ding's sound. The cave is usually 53cm in diameter, 24 cm high and weighs 3.7 kg. It can emit sounds like Udu thanks to Helmholtz resonance (air passing through overlapping metal layers with narrow slits). The cave is also capable of chime like singing bowl. Sometimes this instrument is called "Hang drum", because it is often played in the same way as playing drums, hitting with the hand and because it is related to the type of steel drum. However, in fact, Hang can emit many different sounds, sounds like nothing. Each Cave can be adjusted to its own voice, depending on the user, meaning that it can design its own "sound ring".