Last night we celebrated Walpurgis night, normally associated with big crowds at bonfires, singing and fireworks, a celebration that the winter is gone!
This year a radio channel requested videos of people singing a traditional song, they got 707 videos and mixed together above video.
Source https://sverigesradio.se/artikel/7463654
Walpurgis night: https://en.m.wikipedia.org/wiki/Walpurgis_Night