Violins with five strings
There are two distinctly different types of violins with five strings, which are not related to one another. The first type appeared at the end of the 17th C. in Germany and Austia, often employed in virtuoso contexts. The two most probable tunings were: g-d-g-d-g and a-e-a-e-a, although with the propensity of violinists of these regions to use scordatura (a deliberate mistuning of the violin strings to match the key of the piece), there may well have been other tunings in use.
The second form, called a quinton, appeared in France towards the beginning of the 18th C. and was tuned g-d'-a'-d''-g''. The quinton was in use until the French Revolution.