As told to me by an 85 year old Norwegian folk lady, with a certain twinkle in her eye.
"Why did the Vikings leave their own country and invade parts of Europe and England ....... because they knew that 200 years later the Hardanger fiddle would be invented".
She lived in the Hardanger region and explained that to be a good player you had to be taught by the Trols, so, for three consecutive days you had to throw a leg of lamb into the Hardanger Fiord then the Trols would come out and teach you how to play properly. I met a lot of Norwegian players who had definitely not followed that piece of folk-law. But, played well, what a majical sound, fiords, mountains and mist all rolled into one.