Hi Bevy. This is a super difficult fix. Unlike an air conditioner or a ground buzz that just hangs out there in the same frequency range and volume - so eq will reduce them convincingly - people talking is constantly changing. Plus! most likely it's going to be in the same range as the fiddle, so really harsh eq is going to do as much damage to the instrument as it will to the voices.
Izotope RX has some really good tools that would not completely get rid of the voices, but could definitely help reduce them. I'm sure there are other programs out there that are similar, but RX is the one I'm most familiar with. It's a pretty expensive program for a one time use though. It might be worthwhile finding a mastering engineer who specializes in noise reduction and having a chat with them about what they would charge you.