Knutsen og Ludvigsen are two well-loved Norwegian children's entertainers. They've written dozens of songs and all Norwegians have grown up with their music. One of my favorites is Eventyret av en melodi, which tells the story of a boy who walked along whistling a medoly, which got picked up by birds and school children and city folk and eventually made its way to the king where it became a national sensation. The song is very funny, and they offer 3 possible endings, each one brilliant.
The man who plays the role of Ludvigsen died a few months ago, and there was a national day of mourning. A tribute concert is being planned, and a website is collecting recordings of people singing or humming the melody. They will play them all simultaneously at the concert. Anna's class made a contribution, here's a screenshot from the site.
If you want to hear all the contributors singing the melody together, visit kamfest here.