We are still talking I presume about the 13th century. Am I wrong in thinking by and large the specific people who made records/wrote things down were scribes/clerks who were either part of the elite or specifically employed by them? Monks were often employed in this work. Entertainers might also have done this.

Regarding folk items moving from one language to another, where this does not have a specific form like a ballad the movement could easily be facilitated by any of the 11 methods suggested, and others; likewise where the story of a ballad has moved from one language to another, easy peasy; but something with a specific form like a ballad or similar structured item would surely need to have been a specific translation by a bi-lingual person with an interest in doing so.

Having said that I remember reading about a German ballad being translated into French in the early 19th century, and then presumably into Portuguese as the ballad later became very common in Brazil. Once a ballad has been through a literary process, either translated and published or just published it is remarkable how quickly that ballad can become quite widespread in oral tradition.