A modern recording, obviously. Now where did this come from? It is certainly a very idiomatic thing to do with multiple voices. In fact, at Notre Dame in Paris, in the late 12th century, a fellow named Léonin was doing something similar:
Followed soon after by Pérotin:
And these are just the ones whose names we know. This kind of simple harmony goes back even further. I wonder if the idea could possibly have spread from the Western church--this was all church music--to the Eastern church?
Jon also sent me an example of Mongolian throat singing. I'm going to choose a different one just for the sake of simplicity:
The example Jon suggested was this one:
which is accompanied by long notes in the bowed string instrument. What the singers are doing is using their throats as vibrating columns of air and manipulating them to bring out different overtones. This is the basic principle of wind instruments which use keys to change the length of the column and therefore play chromatic notes. Jon also suggested this example of Bulgarian choral singing:
Now this is pretty interesting: it uses the kinds of complex rhythms that Bartok collected when he researched Bulgarian music in the 1920s. But it also is using some rather unusual harmonies with lots of sustained seconds--an interval that is usually considered dissonant.
I'm sure that there are other examples, but I thank Jon for sending these and for the lengthy commentary that accompanied them.
The Mongolian music aside, the other examples do not seem to pre-date the first polyphonic organum (and therefore first genuine harmony) of Western Europe, which dates from around 1000 AD. So we may be forced to the conclusion that, like accurate music notation, harmony and polyphony were invented exactly once in music history. Even more astonishing, they were both invented at roughly the same time in roughly the same place: southern France, northern Italy around 1000 AD. Nailing down the details of notating rhythms took until about 1500.
Could it be that harmony, counterpoint and the ability to write them down were unique discoveries? It seems a lot of other things were only discovered once and then spread to the rest of the world: paper-making, gunpowder and printing come to mind. But we usually don't think of things like harmony in that category. It just seems that any group of singers getting together would invent harmony out of pure instinct. But no. Pure instinct seems to get you to everyone singing the same thing: monophony. Polyphony doesn't seem to come by instinct.
But I'm not quite sure what to think about those Mongolian guys...