Norway has a distinctive double-strung violin called the Hardanger Fiddle. The joke goes that with a regular fiddle you play on "catgut", but on the
hardingfele, you play on the whole cat.
The late Joe Bethancourt, on
The Naked Banjo, starts off on a gut-strung, fretless, 4-string banjo, brilliantly playing his way through the instrument's evolution on a succession of period instruments and songs. So good, you might forget it's educational.
He uses a silver-strung mail order guitar on
Who Fears the Devil, singing songs from Manley Wade Wellman's stories of Silver John.
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http://www.whitetreeaz.com/</shameless plug>
He also made an SCA Filk album with Leslie Fish,
Serious Steel, among many other interests and accomplishments.