This festival is held every year in Port Townsend, WA, and brings tradition-bearers from all over the US, and beyond, for a week of workshops, band labs, tutorials, jamming, etc. It's a great festival, including for non-fiddlers. This year, the band RéVeillons from Quebec will be on staff, including David Berthiaume on English concertina. There will also be a concertina tutorial, tutor is Janet Dows on anglo. (Tutorials can emphasize repertoire or technique, depending on who attends.)
http://centrum.org/festival-of-american-fiddle-tunes-the-workshop/