What is the difference between a violin and a fiddle, if any?
In terms of structure, the modern versions of these instruments are identical. Sometimes fiddles are said to have a lower bridge*, which slightly reduces the space between the strings and fingerboard, and makes the sound a bit more "harsh”. The main difference, however, is in the repertoire. Serious classical pieces are performed exclusively on the violin. But when the same violin is used to play folk music, it becomes a fiddle. Fiddlers, as a rule, don’t play from music sheets, do a lot of improvising, hold the instrument in unconventional ways and make peculiar (and masterful!) things with it.
Ambrose Bierce in "The Cynic's Word Book" (1906) described the fiddle as “an instrument to tickle human ears by friction of a horse's tail on the entrails of a cat”. That might be quite an accurate description. During our trip to Ireland in May we will attempt to take hold of at least one fiddler**. In the meantime – the amazing Eoghan Neff, a virtuoso fiddler that we met last year in Doolin. This one you need to see, not just hear!
* A thin wooden plate that supports the strings and is mounted on the lower deck of the instrument
** Details of the trip http://www.waysofinspiration.com/walking-with-the-clouds