The woman is singing an ancient herding song of the Vikings, from mid Sweden and Norway.
The singer, Jonna Jinton, said "In the middle of the bright summernight I went out to call for the cows. I thought that maybe, something deep inside them, remember the sounds from the ancient times when people called for them over far distances. They came running, together with a million mosquitos. But what a magical night."
The call is old, but the cows remember. There is something magical in the way that cows respond to music, especially that played or sung by a person, live.
The call is called 'Kulning,' and has been used for hundreds, if not thousands of years.
The cows come wandering over, intrigued and at one point one of the cows actually mounts another one!
The call of the herd is wild, and the cows, even wilder.