Also seeing a pretty clear linguistic link between “vielle” and “fiddle.”

In german it’s Fidel (like Castro). And I’ve been told it’s distinct from “Fiedel” (long I like “feeling”), which describes a cheap but modern violin.

I wonder if the “rough” sound you describe would be at home with various European and North American folk traditions.

Pretty much. Tbh. it was the soundtrack of witcher 3 that got me into folk and early music and making my own instruments.

One step further would be to make an instrument with horsehair as strings, like tagelharpa or кобыз (kobyz)