Before taking Swedish violin lessons, you need to make sure your teacher isn't secretly Näcken. Know the warning signs:

Are they constantly at least slightly damp for no discernable reason?

Do they demand payments in snuff and akvavit?

Did you meet them on an old bridge, the kind they don't make anymore?

Have you caught them in an unguarded moment playing their violin next to a stream while wearing little to no clothes?

Are they sometimes a horse?

If you answered yes to any of these questions, they may be Näcken. Be very careful about playing any song they teach you, once you start playing, it's not a guarantee you'll be able to stop!

Things are much simpler in America, you just need to stay away from Georgia.
@Owlor Yeah, like we got Bigfoot up in the Pacific Northwest but they’re scared of people so the only advisement is “Don’t antagonize them.”

@Urthdigger Swedish folkloric creatures are comparatively more malicious, trolls will straight up just kidnap you, it's a bit of a problem.

Question is, if you meet bigfoot at the crossroads, what sort of instrument would he teach you to play? I imagine he's pretty good at rock drumming.

@Owlor Yeah, colonization drove out most of the more aggressive ones. Save for the deep south and New Jersey. Bigfoot are good at drums, but they’re too skittish to be met at a crossroads. If you’re deep in the woods, far enough to not hear the road, put an ear to the ground and be as still as possible. You may hear one play and pick up a few things.