A traditional Swedish instrument, the nyckelharpa is a keyed fiddle, meaning that it a bow is drawn across its strings while keys are fingered to produce different tones. Depictions of the instrument date to the 14th and 15th centuries in Sweden, Denmark, and Germany. There are about 10,000 nyckelharpa players in Sweden today, due to a resurgence of popularity in the 1960s and 70s.
Here is Bach played on the nyckelharpa. The melody is perfectly matched with the instrument: