I just resumed my Hardanger fiddle lessons.  I'd taken a two-year break because of a combination of the car-crash shoulder injury, and the fact that the grinding stress of the last couple years has turned my brain to mush.

Anyway, hardanger fiddles are cool.

They have eight or nine strings (more traditional fiddles have eight, more modern varieties have nine)  Four top strings, which are bowed, and four or five understrings which resonate in sympathy with the bowed strings.  You often bow two or three strings at once, and use complex multiple fingerings to create elaborate embellishments on the melody.

Come to find out, that the fiddles supposedly came from the trolls, that really good fiddlers were often reputed to be taught by the devil, and that Hardanger fiddles were burned by Christians.

(Here's another source, and a quote:)

Because of the association with dark magic, thousands of fiddles were burned or destroyed by religious fanatics throughout the 19th century. This is one of the primary reasons that today's fiddlers have more contemporary instruments. It is also the reason that the few existing old ones are kept in sealed cases, like biological specimens.

Grump.  First Science Fiction and rock and roll, then Martial Arts, then Yoga...now the hardanger fiddle.

How come the devil gets all the cool stuff?

More about the legends from this site:

Legends

Some hardingfele tunes are rhythmically very complex. The springar, though basically in 3/4, appears virtually impenetrable, with beats which vary widely in length; it is nevertheless a dance tune and is accompanied by foot stamping. More accessible are the different types of walking tune, from the slow march to the gangar, a steady 2/4 or 6/8. The halling is another 2/4 tune, played for a solo dance where a man attempts to leap high enough to kick a hat off a stick held by a girl. The origin of some of these old tunes is cloaked in legend. Some come from the troll or Nacken who lives in lakes, waterfalls and streams; if you hang your fiddle overnight under a bridge where he lives, the troll will retune your fiddle and play a tune on it, finally leaving his own instrument next to it. If on returning you pick up your own fiddle, the troll's tune and supernatural touch will beyours . If by mistake you pick up the troll's fiddle, your soul is his forever!

Rammeslatter are tunes which, because of their hypnotic quality can put player and listener alike into a state of trance; the fiddler will play, unable to stop, until someone drags the fiddle from his hands. It is said that fanitullen, the devil's tune, was first played by the man himself who appeared, hooves and all, at a village dance. He grabbed the fiddle and began playing a tune so wonderful that the gathered people continued dancing until they died from exhaustion- and then their corpses continued dancing until their skulls rolled out of the door and down the hill!

Another group of tunes, the Gammeldans, were imported from Sweden in the 19th century; these tend to be more predictable and less mysterious and melancholy. The mazurka has a bouncy 3/4 rhythm (eg. Brage Gilles Mazurka ); a similar dotted rhythm, but in 4/4 is found in the schottische (eg. Schottis fran (from) Lima .) Polkas, (not to be confused with polskas) and Reinlenders have a jolly 2/4 rhythm. Sweden has its equivalent to the walking tunes of Norway, including the brudmarsch (wedding march) and the ganglat. Gardeby Laten is a ganglat so often played that people sing along with it words which mean "aren't you sick of this tune yet?". Also well known is Appelbo Ganglat .

Probably the most important group of Swedish tunes are the polskas. These have a 3/4 rhythm with stress on the first and third beats; the emphasis of these beats varies considerably from region to region. Polskas, and indeed many Scandinavian tunes, are often named after a revered fiddler from the past whose playing defined a particular tune, though he is unlikely to have actually written it; for example Polska efter (after) Karl Linblad, or Polska e. Per Osa . Very useful for the fiddler is the skanklåt- an "I want to get paid " tune which reminds the guests at a wedding that the poor musician has been playing for five hours, hasn't been offered any sandwiches, hasn't been paid, and wants to go home.

Most of the above Swedish and gammeldans tunes are played on the normal fiddle (called flatfele in Norway), often in ensembles with other instruments such as accordion, recorder, or fattigmannsfele (poor man's fiddle)- the jew's harp. Spellmannslag are large groups of fiddlers who meet regularly to learn, play for enjoyment, and maintain the tradition.