> I'm curious about this myself. For some reason, it seems as if I have
> heard the strain they are singing before, as if it was a national anthem.
> However, the Soviet Union's National Anthem did not include that
> particular strain so I'm stumped!
According to Aaron Ahles (on a YouTube comment):
"The tune that starts around 4:54 is from Rimsky-Korsakov's 'Russian Easter Festival Overture' which in and of itself is taken from the traditional Russian Orthodox chant "Let God Rise"