Good luck with this. And do take account of the "Greater Scandinavia" music. I'm particularly thinking of the areas I know, Orkney, Shetland(Scotland), Isle of Man, and the bit I know best, Cumbrian fiddle music (NW England).All Norse dominated in the past.The sea has always been a great means of communication in those parts.
Send me a personal message if you'ld like info on links to Cumbrian music sites (or find me via the Boat Band,via harbourtownrecords.com website.