Traditional sub-Saharan African harmony is a music theory of harmony in Sub-Saharan Africa music based on the principles of homophonic parallelism (chords based around a leading melody that follow its rhythm and contour), homophonic polyphony (independent parts moving together), counter melody (secondary melody) and ostinato-variation (variations based on a repeated theme). Polyphony (contrapuntal and ostinato variation) is common in African music and heterophony (the voices move at different times) is a common technique as well. Although these principles of traditional (precolonial and pre-Arab) African music are of Pan-African validity, the degree to which they are used in one area over another (or in the same community) varies. Specific techniques that used to generate harmony in Africa