The noted anthropologist Edward Sapir wrote as follows regarding such patterns:
Thus, it would appear that the tradition of polyphonic vocalization pointed to by Jordania is likely to have pervaded much of Europe at some time in the distant past, prior to the advent, during a later period, of the monophonic/unison tradition destined to marginalize it. As we've learned, Jordania, following Gimbutas, associates such polyphony with "Old European" culture, and "monophony" with the migration into Europe of a more agressive, and successful, "proto Indo-european" culture. But the situation isn't quite that simple, because there is more than one type of traditional polyphonic singing in Europe, and each, as Jordania notes, is distributed somewhat differently. In what follows, I'll be drawing on information gleaned from Jordania's book, but with a somewhat different interpretation.
For chronological purposes, cases of the interrupted distribution of a culture element are of particular importance. In a general way, a culture element whose area of distribution is a broken one must be considered as of older date, other things being equal, than a culture element diffused over an equivalent but continuous area. The reason for this is that in the former case we have to add to the lapse of time allowed for the diffusion of the element over its area of distribution the time taken to bring about the present isolation of the two areas, a time which may vary from a few years or a generation to a number of centuries. . . [T]he interrupted distribution of a culture element gives us a minimum relative date for the origin of the culture element itself. The element must have arisen prior to the event or series of events that resulted in the geographical isolation of the two areas ("Time Perspective in Aboriginal American Culture, a Study in Method." Geological Survey Memoir 90: No. 13, Anthropological Series. Ottawa: Government Printing Bureau (1916), p. 41).
I want for now to focus on three of the most important types of traditional polyphonic vocalization in Europe: 1. Drone polyphony (one voice holding or repeating the same tone as one or more others sing melodically along with it), usually emphasing intervals of the 4th and 5th -- and, in many cases, dissonances based on both major and minor seconds; 2. parallel polyphony, sometimes in 4ths and 5ths, but also, in certain areas, 3rds and 6ths; 3. "contrapuntal" polyphony, involving two or more rhymically and melodically independent voices.
All I have time for today. Stay tuned.