The violin is a bowed string instrument with four strings tuned in perfect fifths. It is the smallest and highest-pitched member of the violin family of string instruments, which also includes the viola and cello. A violin is called a fiddle when playing folk music. A "fiddle" is also a colloquial term for instruments used by players in all genres, including classical music. Fiddle playing, or fiddling, is a style of music.
edit Physical Structure
Both a fiddle and a violin are alike in physical appearance. Indeed, the exact same instrument may be played as a violin or fiddle, it is almost completely an issue of style and intent.
A very recent development in modern instruments is the introduction of the 5-string Fiddle. It includes a lower 5th (Viola) C-String, left and below the G string. This change has not been reproduced for the violin.
Another common difference may be the preference of synthetic polymer strings by most classical violinists, whereas some fiddle players like the newer steel core strings for the sharper, crisper sound.
Historically, the term Fiddle describes the modern day Violin. Like the Violin this instrument also had four strings. Now both are used but in making different genres of music.
The intent or purpose of the Fiddle and Violin are completely different.
The Violinist reproduces the composer’s music with exacting accuracy, down to the loudness of individual notes. A properly performed violin piece will not deviate in the slightest degree from the composer's notation of the music. This is also how a symphony can pull off having 50 or more musicians performing in exact unison.
Fiddlers on the other hand, bring their own interpretation to every piece, sometimes varying so far from the original melody, as to make it almost unrecognizable.
This cannot be interpreted to indicate either style of play derives any less intensity or greatness from the talent of the performers, indeed, both violin and fiddle style benefit greatly from the talent of the performer.
edit Differences in Playing Style and Technique
When played in a folk style, then it is said to be a fiddle while when played in classical tones then it is a Violin. In fact, the playing style is a major criteria that differs the fiddle from the violin.
Some untrained fiddlers may not hold the instrument firmly between the chin and shoulder, and instead rest the instrument on their chest. This greatly reduces the playability of the instrument and is never seen in violin performance.
The violin almost always appears in orchestral, symphonic or chamber settings with other violins, violas, cellos, and double basses or symphonic horns.
The Fiddle on the other hand may be accompanied by a wide range of instruments, including but not limited to: mandolin, guitar, drums, mountain dulcimer, banjo, electronic keyboard, dobro
Bowed string instruments are among the most difficult instruments to learn because the tone quality will degrade quickly in unpracticed hands. While it may be said that violinist have a higher need for professional training due to the exacting nature of excellent performance, this cannot, by any means, be interpreted to infer that the either style is more or less difficult to play.
How to play the fiddle: