Umm allright, you need to buy me a big beer because I still want to help you Krzysiek :D Here I prepared some ballads from the 70's
Janusz Laskowski "Siedem dziewcząt z Albatrosa"
Czerwone gitary "Historia jednej znajomości"
Czesław Niemen "Dziwny jest ten świat"
I'll think of some others if you won't like any of these though I think Czesław Niemen is a good idea :)
Maybe Czerwone Gitary? Check Anna Maria
or this one but it's kinda boring in my opinion hah, found a link for you: