I wonder wonder how many were carried by wandering* traders and tradesmen for whom a good voice and repertoire of songs might engender hospitality, perhaps rather than suspicion as a stranger.

David Thomson describes travelling tailors in Ireland (early twentieth century) in People of the Sea. They would make clothes in people's homes, in remote rural areas, and were usually housed in the loft where they could hear everything that was said in the house. They had a reputation as singers and storytellers (which would make them welcome to stay longer and maybe generate more work), and listening from up there would help expand their repertoire. But not much multilingualism involved, though presumably some between English and Irish.