Strings!
Instruments- discuss specific features, luthiers, instrument problems & questions
Hey @notsothoreau, I agree with what Richard has said. Initially follow whatever recommendations the luthier has for your instrument. But you should also experiment a little to discover your own preferences. You may find that you want one or more strings a little heavier or lighter than what the luthier suggested. And you may find that different dulcimers respond differently to different string gauges. Learn what you prefer for each of your dulcimers and then you can buy single strings in bulk.
As Richard says, in general, nickel-wound strings have a brighter sound and bronze-wound strings have a mellower sound. I much prefer bronze-wound strings, but that is a matter of personal preference. I also use so-called "squeekless" strings for my bass strings. They reduce the sound of your fingers sliding up and down. If you play in a drone style and don't fret the bass string, that is obviously not an issue for you. And some people don't like some of the squeekless strings because those that are coated with a plastic to fill in the grooves supposedly have a muted sound (something my ears don't hear).
You might also want to make use of the Strothers String Gauge Calculator . You enter in the VSL (vibrating string length, or the distance between the nut and the bridge) and the note you want the open string to play. The calculator will then estimate a good string gauge to use. Note that the calculator errs on the light side, so feel free to try out stings one or two notches heavier than indicated.
Just think of this as one area you can explore to help develop your own preferences and thereby, your own sound.
updated by @dusty: 04/01/18 01:25:21PM

But thanks for passing on the news.