I myself got to know the nyckelharpa when I lived in Sweden, and I had always assumed that it was also originally a Swedish instrument, used to Swedish folk music....until I met fellow nyckelharpists in Holland, who later would become my colleagues in the Dutch nyckelharpa quartet Resonans. For some of them it was not a Swedish instrument at all; it belonged to early music (or Early Music?, I mean: music from before 1750 from all kinds of countries, say from Machaut to Bach). Why Swedish?
Well-known forefighters of this, for me surprising, idea of the harpa are professionals such as Marco Ambrosini, Didier François, Annette Osann and Jule Bauer. They also regularly collaborate with early music departments of conservatories, and with well-known baroque ensembles. To support their ideas about the origin of the harpa, they often refer to old paintings. The angel in the church in Siena from the early 15th century is an example:
Enkelharpa, model from the early 17th century
From 1930, first August Bohlin and later Eric Sahlström developed the well-known chromatic nyckelharpa with three playing strings. So we are dealing with a truly modern instrument! Bohlin and Sahlström based themselves entirely on the silverbasharpa: they kept the low bourdon string and in fact only put tangents and keys on the second lowest, the G. They also kept the tuning of the two highest playing strings at "silverbas height": C and A.
.
August Bohlin on the left, Eric Sahlström on the right
I will write about this "C tuning" later. It is interesting to note that both these two harpa innovators were violinists. So though they were totally used to fifths tuning, they kept their new instruments in silverbas tuning, C G C' A'.
After Sahlström, development continued - but more and more outside Sweden. In Germany and France, builders began developing nyckelharpas with keys on all four strings. They also built harpas with lower or higher tuning. Esbjörn Hogmark writes in his book "Nyckelharpa" (which unfortunately only appeared in Swedish) that he is inclined to say with some disdain that "people in Sweden know why keys on the low C is not such a good idea", but Swedish builders have now also, hesitantly, started with four rows, oktavharpor and fiolharpor. And that tones on the low C string would not sound good on a chromatic harpa is completely belied by the non-Swedish instruments of e.g. Condi, Mayr and Osann. And actually, the first four row harpa was built by a Swede, Erik Olsson in Hedemora, during the 1950s! Yet he seems to have been out too early.
How Swedish is the nyckelharpa? Very Swedish, I would say, and even enigmatically Uppländsk. Which does not alter the fact that the sound is ideally suited for some genres other than (Swedish) folk music. In fact, I hope and expect that the automatical "tying" of nyckelharpa and Swedish music eventually will disappear. Also, the initiative in the world of harpa building is now largely found outside Sweden. And indeed, it is especially a pleasure to play old music on a harpa!