@Xekoslav Thanks, Svarica sounds good enough indeed! As for the folk music, while researching, I stumbled upon a style called “ganga”, which is closer to what I’m looking for, since it sounds more archaic. Unfortunately, couldn’t find any good enough performances of it either (usually only live stuff with bad recording or cut off). Oh, well, truly authentic music seems to be impossible to get anyway, not in modern recordings at least.

@Shaokang Wait, is Trag Serbian or Croatian? I have one or two albums of theirs from before, but I already found quite a bit of good folk-atmospheric music from Serbia (Pavle Aksentijevic i grupa Zapis sound both good and, in some cases, quite medievalish). Besides Ansambl Renesans’ Skomraska igra, I’ve also added Rasti, rasti moj zeleni bore (the non-Nemanjic version, since the mod is set in the 9th-11th c.), which sounds absolutely awesome. Too bad that many of the really good folk songs reference the Ottoman invasion and thus I can’t use them. That’s why I was looking more for instrumental folk, of which I gathered a good amount from Bulgaria and Serbia, but Croatian one seems to consist mostly of tamburashi (and the rare gusle performances, of course, include singing, are usually too long, bad quality and reference later times as well).