Polyphony ( ) is a type of musical texture consisting of two or more simultaneous lines of independent melody, as opposed to a musical texture with just one voice, monophony, or a texture with one dominant melodic voice accompanied by chords, homophony. Within the context of the Western musical tradition, the term polyphony is usually used to refer to music of the late Middle Ages and Renaissance. Baroque forms such as fugue, which might be called polyphonic, are usually described instead as contrapuntal. Also, as opposed to the species terminology of counterpoint, polyphony was generally either "pitch-against-pitch" / "point-against-point" or "sustained-pitch" in one part with melismas of varying lengths in another. In all cases the conception was probably what Margaret Bent (1999) calls "dyadic counterpoint", with each part being written generally against one other part, with all parts modified if needed in the end. This point-against-point conception is opposed to "successive composition", where voices were written in an order with each new voice fitting into the whole so far constructed, which was previously assumed. The term polyphony is also sometimes used more broadly, to describe any musical texture that is not monophonic. Such a perspective considers homophony as a sub-type of polyphony. Origins Traditional (non-professional) polyphony has a wide, if uneven, distribution among the peoples of the world. Most polyphonic regions of the world are in sub-Saharan Africa, Europe and Oceania. It is believed that the origins of polyphony in traditional music vastly predate the emergence of polyphony in European professional music. Currently there are two contradictory approaches to the problem of the origins of vocal polyphony: the Cultural Model, and the Evolutionary Model. According to the Cultural Model, the origins of polyphony are connected to the development of human musical culture; polyphony came as the natural development of the primordial monophonic singing; therefore polyphonic traditions are bound to gradually replace monophonic traditions. According to the Evolutionary Model, the origins of polyphonic singing are much deeper, and are connected to the earlier stages of human evolution; polyphony was an important part of a defence system of the hominids, and traditions of polyphony are gradually disappearing all over the world. Although the exact origins of polyphony in the Western church traditions are unknown, the treatises Musica enchiriadis and Scolica enchiriadis, both dating from c. 900, are usually considered the oldest extant written examples of polyphony. These treatises provided examples of two-voice