In addition to playing the fiddle, I also write tunes for it. If you're looking for some sort of magic formula, there isn't one*, I just played the old tunes until I started spitting back new ones, and I wrote down the spit (?) that sounded good.

     In spite of my FOSS attempts, the note editor of choice is--well, actually it's a pencil and manuscript paper, but the software of choice is Finale (the free version--I can't afford the expensive one) which I love.

I plan to make most of them available on this website, but haven't yet. Meanwhile, here's one.
Tune (C) 2008 T. Macdonald