Generally speaking, a pygmy is anything of unusually small size. This can be, for example, an animal (such as the pygmy hippopotamus).
In an anthropological context, a Pygmy is specifically a member of one of the hunter-gatherer peoples living in equatorial rainforests characterised by their short height (below one and a half metres on average). Pygmies are found throughout central Africa, with smaller numbers in south-east Asia. The most closely studied group are the Mbuti of the Ituri rainforest in the Democratic Republic of the Congo, which were the subject of a study by Colin Turnbull (The Forest People (1962)). Among the other African groups are the Aka, Baka, Binga, Efé, and Twa.
The African Pygmies are particularly known for their usually vocal music, usually characterised by dense contrapuntal communal improvisation. Simha Arom says that the level of polyphonic complexity of Pygmy music was reached in Europe in the 14th century, yet Pygmy culture is unwritten and ancient, some Pygmy groups being the first know cultures in some areas of Africa. Music permeates daily life and there are songs for entertainment as well as specific events and activities.
Formally the music consists of at most only four parts, and can be described as an, "ostinato with variations," or similar to a passacaglia, in that it is cycical. In fact its based on repitition of periods of equal length, which each singer divides using different rhythmic figures specific to different repetoires. This interesting case of Ethnomusicology and Ethnomathematics creates a detailed surface and endless variations of not only the same period repeated, but the same piece of music. As in some Balinese gamelan these patterns are based based on a super-pattern which is never heard. The Pygmies themselves do not learn or think of their music in this theoretical framework, but learn the music growing up.