Sutartinės (from the word "sutarti"—to be in concordance, in agreement, singular "sutartinė") are highly unique examples of folk music. They are an ancient form of two and three voiced polyphony, based on the oldest principles of multivoiced vocal music: heterophony, parallelism, canon and free imitation. Most of the sutartinės' repertoire was recorded in the 19th and 20th centuries, but sources from the 16th century on show that they were significant along with monophonic songs. At present the sutartinės have almost become extinct as a genre among the population, but they are fostered by many Lithuanian folklore ensembles.