Name of the beautiful song??

There's a song before to the scene of the Szczuka's assasination, in which there's Maciek talking with another man and in the background is heard a song at the reception. There's the scene that i'm talking about: https://www.youtube.com/watch?v=EDsW14Wqu98 What's the name of that song?? Bring me a lot of memories and a good feeling that cannot describe, it's part of the soundtrack of the movie or a polish symphony??