What is heterophony in Bulgarian, Serbian, and Croatian folk song?

In the context of folk music, heterophony is a musical texture defined by the simultaneous performance of melodic variants of the same tune. In Bulgarian, Serbian, and Croatian folk traditions, this technique is a significant element of song, occurring when two singers—or a singer and their accompanying instrument—perform slightly different versions of the same melody at the same time.12

A prominent example of this practice is found in the tradition of Balkan Slavic epic singers, who accompany themselves heterophonically on the gusle, a one- or two-stringed fiddle. While the gusle is the traditional instrument for this accompaniment, the specific melodic variations produced can depend on regional micro-traditions and the individual performance preferences of the singer, known as a guslar.13

Beyond heterophony, these Slavic regions also utilize other forms of polyphony, such as parallel singing in seconds, fourths, and fifths, which are characteristic of the area.2