My favourite songs (it is the first song that I have arranged for dulcimer) is "Pretty Polly".
I play it on Daa tuning with the Capo on the 1° fret (this way I can play on the "minor" modes).
Just last week I arranged (same tuning and Capo) an ancient French song: "Belle qui tiens ma vie".

On dulcimer you can play more or less everything, just try to change tuning (or use the capo) for to find the right mode and... fret the strings with your fingers.

Marco.