Bartók recording folk music. His subject sings into the horn of an Edison phonograph, which incised a cylinder disk with a needle.
Bela Bartók was one of the earliest ethnomusicologists.
Here is a field recording he made of Romanian folk dances.
Here is his piano composition entitle Romanian Folk Dances.
Here is a folk song he recorded:
The same piece, transcribed for two violins:
A piece by Bartók, based on a folk song he transcribed in Slovakia: