The key box design is very simple (thank you Kjell Lundvall for the suggestion). It’s even more simple than the design used in old kontrabas nyckelharpor I have seen in photos; rather than having a double wall on the side of the box away from the “finger” side of the keys, it has a single wall, with the key body able to poke through. I have seen this idea in four row chromatic nyckelharpor as well – presumably to make the keybox for that instrument, which has to be rather bulky anyway, a bit less so.
Here are the sides after being marked out carefully:
I used a spreadsheet to keep details of the measurements, so that I was easily able to check and make changes. In particular, I have moved some of the keys at the high note end so that they don’t have to be quite so thin. They are still in suitable places for their tangents, of course. (The tangents are the little movable frets that the key pushes against the string. They are called “leaves” in Swedish.)
This kontrabas nyckelharpa is going to have some quarter notes on it (should be fun!). They are keyed using a lower row of just three keys; for simplicity the slots for these keys are cut as holes, rather than making the keybox sides more complicated by slicing them up. I made a 6mm by 14mm gauge block to check the hole sizes; they are filed carefully to the right size.
The photo above shows the gauge block in use.
It’s quite painstaking work to cut the key slots using hand tools. I use a fine toothed hacksaw, a chisel to hack out the bulk of the waste, and files to finish the surfaces. My chisel collection is mostly of chisels that belonged to my grandfather; he was a carpenter who built railway wagons.
Here’s a completed side with a couple of the old chisels. I have my grandfather’s oilstone as well, for sharpening them. I was taught how to do these things in woodwork classes at school, many years ago!
After a bit more work both sides were finished, and the “feet” made to attach the sides to the neck. It was easier to do this than to try to make each side, with its foot, out of a single piece of wood. The feet will be glued on as well as screwed.
Here are the two sides assembled; the holes in the feet for attachment to the neck are already drilled and countersunk.
That completes the keybox.