Drömmen om Elin
Drömmen om Elin, “The Dream of Elin”, is a popular Swedish waltz/song by Carl Jularbo. Jularbo was a celebrated accordionist and bandleader in the first half of the 20th century. He was internationally famous, and made many recordings throughout his career.
The type of tune is gammaldans, “old-time dance”, and does not fall into a regional fiddle dialect, as most fiddle tunes do. Gammaldans pieces are somewhat generic, being played the same way everywhere.
Drömmen om Elin is one of the best known tunes in Sweden. Traditional fiddlers seldom initiate playing it in a fiddle jam, but know it well enough in their heads to play along with it if it gets started.
It is mostly considered an accordion tune, though. I went through scores of YouTube videos before I found one with fiddlers playing it – but even then, there were 3 fiddles, 3 guitars, a bass, and 8 accordions jamming at a festival. You can see the video here.