Having no formal music training, I use the Deckman mode of figuring what's "modal"...but if all diatonic music is in one mode or another, what makes the Deckman sort sound so different, and what mode is it, then. I have both a guitar and a dulcimer. The May Carol, for instance, sounds definitely "modal" to me, and played on a guitar needs a Dm, a C and an Am, for instance. So far, I've been not been able to find a dulcimer mode to play this in, maybe because I only know Mix, Aolian, and Ionian. Gregorian chants also sound "modal" to me...is it just one mode that has that odd, moody sound?

I have as much trouble understanding music theory as I do higher mathmatics....