Hello, besides the plain gut soltion there is the possibility to use a violin-e for the d'' and a viola d' for d'
I used to use a Pirastro Eudoxa violin-e for d'' and a Thomastik spirocore viola-d strong. Nigel Eaton once recomended a Corelli Crystal viola-d.
With the drones, I would replace the mouche with the former c drone now in d, let the G drone be a G done and buy a string for the low D (usually nearly the same diameter as the G drone. This gives you drones on the bottom of the keyboard and alternatively at the third diatonic key.
kind regards, Simon -- http://simonwascher.info
