Early models of the modern chromatic nyckelharpa existed even in the Middle Ages. While most images of it are to be found in Sweden, there are also some in Denmark, Germany, Austria and Italy. In the Renaissance period, Agricola and Praetorius (syntagma Musicum 1619) make reference to the “key fiddle” in texts and images.
After the baroque period, reference to nyckelharpa music or to existing instruments was only to be found in Sweden but it is only in the folk music of the Uppland region that there is evidence of an unbroken tradition of nyckelharpa-playing.
The traditional Swedish nyckelharpa types (gammelharpor) were instruments with one or two melody strings and with drones. It is not clear when the sympathetic strings were added.
In 1929 August Bohlin (1886-1949) developed the chromatic three-row nyckelharpa which had up to 12 sympathetic strings but it is thanks mainly to Eric Sahlström (1912-1986) that the almost obsolete nyckelharpa has enjoyed renewed popularity since the 1970s.
For a long time the chromatic nyckelharpa and some types of gammelharpa (kontrabasharpa, silverbasharpa) were predominantly played in Sweden in the context of local folk music, but meanwhile the nyckelharpa is also played outside of Sweden and in a non-folklore repertoire (ranging from mediaeval, renaissance and baroque to modern music). One result of the widening of the repertoire has been that a fourth row of keys has been added by instrument makers particularly in Germany and France. On the three-row harpa the lowest playing string is just a bass or drone string.
The modern three-row or four-row nyckelharpa is a very versatile instrument which can be integrated in a variety of different music styles.