Another definition I heard is that a fiddler is just a sloppy violinist and a violinist is a fancy fiddler.

I dont actually believe that - I went through years of classical training and stopped playing for 15yrs and 4 years ago took up the fiddle with a passion. It was definitely an advantage to have the intonation and the training - I only wish Id been introduced to fiddle music back then.

I agree with the above points on playing more open strings in fiddle music as the ringing of other strings in harmony is a big part. Also there are some ornaments such as slides and double stops which are not common in classical music - but vibrato, pizzicato spicato etc. do not occur much in fiddle music. The bowing too - it is funny watching classical violinists trying to play fiddle style with long bow strokes. On another note, a friend of mine with classical training but also a fiddle player has noticed a certain bias against classicaly trained players in old time competitions.

Cheers Petr