This study represents a thorough investigation of a polyphonic vocal village tradition in Bistritsa, Bulgaria. Outsiders describe the narrow intervals of these songs as being "maximally rough", while the singers themselves experience their performance as smooth, beautiful and pleasant. Almost identical polyphonic traditions can be found in places sometimes thousands of kilometers apart. This inquiry is carried out within a very broad and comparative context, whereby historical sources, the origin of different constituents and etymologies as well as electronic sound analysis are taken into account. The results are stunning and ever more relevant - and not just for ethnomusicologists: The babi or grannies of Bistritsa and their songs have been inscribed on UNESCO's List of Intangible Cultural Heritage of Mankind in 2008.