Recently made my first Symphonia and just used 2mm wire in the keys as tangents. Metal tangents are pricey, wood tangents are difficult to cut, but some makers use twisted wire and it seems to work fine, they are screwed to the key and can be rotated to tune the contact with the string sharp or flat.
Use round nose pliers to make a loop on the end of the wire, centre the loop, hammer it flat, bend it at right angles to the wire and screw it to the key carefully having drilled a hole large enough that the screw will not split the wood.
![](https://s2.save4k.ru/pic/2-lEcLWsVjk/maxresdefault.jpg)