Georgia has one of the world's most ancient polyphonic singing traditions. Polyphony refers to music where each vocal line is equally important, sharing the melody among them; (as opposed to homophony, in which melodic interest is concentrated in a single line). The singing tradition in the Caucasus is unique in its harmonic and -- especially in western Georgia -- its extreme polyphonic approach. Many songs have distinct archaic traits dating from pre-Christian times, and in most traditional music the intervals are flexible and do not coincide with tempered scale intervals (with the exception of the fifth). The harmonies are unlike anything in European music, with untempered intervals and striking harmonic convergences.