Like Celtic music, it has tonality that is very foreign to conventional Western music, but it is not Celtic; it is native Polish. Some of their instruments, like the suka fiddle, are known from nowhere else, and the biały głos ("white voice") singing they often use is characteristic of many places in Eastern Europe.
The cellist and lead singer, Maja Kleszcz, has a wonderful voice with great versatility. She also sings jazz with her incarNations project.
Great stuff, thanks for sharing. Warsaw Village Band has a mission of keeping Polish folk music alive.