Djembe drums originated in Africa and are goblet shaped. They are commonly about 12" in diameter and 24" high, but there are some which are up to 18" in diameter.
To produce different tones of the djembe, variations in wood, thickness and skin are all contributing factors. In technical terms, the rounded shape with the extended tube of the djembe body forms a device known in acoustic physics as a "Helmholtz Resonator" which is responsible for that deep rich bass tone.
The main notes produced by the djembe are known as bass, tone or slap and more accomplished players can achieve a borad mix of each.